Mobile telephones can be an excellent tool for keeping in touch while travelling.

Check charges in advance Many companies inflict painful rates for calls when "roaming" outside the home area. Travellers have encountered huge bills for post-paid cell phone service, particularly mobile data. That streaming video download which inexplicably cost hundreds of dollars on a roaming smartphone may be cheaper on a local prepaid handset/SIM and could even be free at a Wi-Fi hotspot.

The main ways you can use a cell phone while travelling overseas include:

1. Taking your phone and SIM card, and use the foreign network (roaming)
2. Purchasing a SIM card at your destination, and put it in your own phone
3. Renting or purchasing a phone and SIM card at your destination
4. Renting or purchasing an international cell phone and SIM card prior to departure

Depending on the length of your trip, it may make sense to buy a local pre-paid mobile telephone at destination or a local SIM card for use in your existing mobile device.

Roaming with your existing phone may be manageable when visiting one European Union country from another, but further abroad the cost may be prohibitive or the service not available. In most of Europe a pre-paid SIM card is usually very cheap (€10 or less with some credit included), although in some countries (e.g. Italy) identification and a local tax code may be necessary. In some countries, such as Mexico, there are roaming charges even within the same country. If you buy a local SIM-card, make sure it is possible to use it without roaming in all places you want to visit.

Bring your phone

The beautiful thing about standards is that there are so many to choose from. There is a vast selection of mobile networks and handsets that not only aren't on the same wavelength, but aren't even speaking the same digital language.

At home, most users select a carrier and then choose a handset which will work with that carrier. The same approach may work while abroad if the traveller buys a low-end prepaid handset at destination and stores it away forgotten at the end of a trip.

Bringing a mobile handset from home for use on a local network abroad is a bit more complicated, especially if one intends to purchase a local SIM (a small card inserted into a GSM or UMTS handset to give it a local number from a provider at the destination).

There are various "generations" of mobile telephone which contain multiple, sometimes-incompatible standards:

• 1G was analogue mobile phone services, such as NMT and AMPS, shut off circa 2008. Now dead.
• 2G is the first batch of digital mobile phones. There are at least two standards which do not interoperate at all:
  • GSM is the most widely used mobile phone standard in the world, originating in Europe. In North America it's supported by AT&T, T-Mobile and Rogers. A GSM-only handset will not work with a CDMA network, and vice-versa.
  • CDMA is a standard used foremost by a few incumbent North American telephone companies: Verizon, Sprint, Bell Canada. Canadian telcos are slowly phasing this out in favour of 3G UMTS (W-CDMA); it's already dead in Telus and TBayTel territory. If your phone type is CDMA, it is unlikely to roam outside of the Americas, Japan and Korea.
• 3G is a later standardisation on UMTS or its variants. W-CDMA is the original version of UMTS; HSPA/HSPDA and HSPA+ are UMTS upgraded for faster Internet data downloads. As many carriers gradually replace GSM or CDMA, a handset with 3G is likely to work abroad in places where GSM-only handsets do not.
  • As the concept of a "generation" of mobile handsets is largely defined by marketers, some advertise EVDO (a faster CDMA) or EDGE (a faster GSM) as "third generation", "3G" or "3x". These standards are not UMTS; the respective incompatibility issues of CDMA vs. GSM all remain in EVDO and EDGE.
  • The same blurred boundaries between "generations" exist with HSPA+ (a faster 3G UMTS branded occasionally as 3.5G or 4G).
• 4G is a faster data connection (usually LTE) available in major cities and supported by a few high-end, Internet-aware handsets. Frequency bands vary; some handsets support half a dozen options. As of 2014, all 4G providers or handsets also support 3G standards; most handsets can also fall back to GSM if the network supports it.
  • WiMax (Sprint USA, some Russian carriers) and TD-LTE (in China) are 4G but not compatible with standard LTE.

There are also multiple frequencies. A handset which lacks the local frequencies or does not use a compatible standard will not connect to the network.

Outside the Americas:

• 900 MHz and 1800 MHz are the most common GSM frequencies
• 900 MHz and 2100 MHz are the most common 3G (UMTS) frequencies
• In Australia, GSM is 900 MHz (Optus/Vodafone/Telstra) with 1800 MHz used for 4G. 850 MHz provides good 3G UMTS (Telstra) coverage.

In the Americas (ITU zone 2):

• 850 MHz and 1900 MHz, the most common GSM or CDMA frequencies, are used for 3G (UMTS) on AT&T and all Canadian major carriers (Bell, Rogers, Telus)
• 1700 MHz and 2100 MHz are used for 3G (UMTS) on the US T-Mobile network
• 1700 MHz is used for Canadian new entrants (Wind, Mobilicity), regional carriers (Eastlink, Vidéotron) and 4G (LTE) services.
• Additional bands (such as 2600 MHz) may be used for 4G LTE to carry high-speed data

If your phone matches all frequencies in the destination country, it should receive a good signal when roaming. If your phone only matches one of the frequencies, it may only work in some locations. An unlocked 3G UMTS "quad band" handset (typically 850/1900 and 900/2100 MHz) is likely to work in much of the world, but read the fine print in the product specifications - some support North American frequencies on GSM only, so won't work on all carriers. Small "new entrant" carriers often deploy on otherwise rarely-used frequencies, which limits the selection of compatible handsets. There are 3G "penta band" handsets (quad-band GSM on 850/1900 and 900/1800 MHz, five bands of UMTS on 1700, 850/1900 and 900/2100 MHz) but these are rare; some add 2600 MHz as a sixth band on 4G LTE only.

The last thing to check is the SIM (subscriber identity module), a small card which assigns a carrier and telephone number to a handset. There are two options for using your existing handset abroad:

• Roaming leaves your existing SIM and carrier in place, relying on agreements between your home carrier and a carrier at your destination to route calls using your existing mobile telephone number. This gets expensive, as billing goes through two telephone companies; any calls to you have to go to your home country first, then back out internationally, further inflating cost. This may be a viable option if visiting one European Union country from elsewhere within the EU, as regulators have cracked down on the worst of the billing abuses. Elsewhere, it can be costly and normally will not be permitted at all on prepaid cash mobile plans. In some cases there may even be roaming surcharges without crossing national boundaries. This is especially true in countries with weak regulations or where one or a handful of companies have "cornered" the market; regional carrier handsets may "roam" when taken to domestic locations outside a limited home region.
• Obtaining a local SIM allows the traveller to obtain a local prepaid plan with a local mobile telephone number at local prices. This won't work if a handset has been "locked" to only accept one provider, although codes to unlock many common handsets may be purchased from third-party sites online.

A few handsets are made specifically for use with multiple providers. These are known as "dual SIM" as they have two card slots; some are effectively two-line phones on which each virtual line can be subscribed to a different number, different provider or different country. The capabilities of these devices vary. While some provide the full capability of two independent devices, some only allow one of the two cards to be active at once, some may be GSM-only on the second card, some may be "quad band" on GSM but be missing the North American UMTS/3G frequencies.

Be cautious with on-line or mail-order vendors; as manufacturers produce multiple, similarly-named handsets on completely different standards, web descriptions often are incorrect, erroneous, not matched to box specs of the handset being shipped or self-contradictory. The handset looks promising on the website, but the box that arrives in the post has some other country's frequencies marked on the package as the phone was manufactured for an overseas market.

A few low-end "dual SIM" handsets are GSM-only. In Canada, only one of three major carriers supports GSM at all, so in Sept-Îles, Baie-Comeau and every Newfoundland outport the GSM-only handset finds no signal.

Roaming

Using your phone in places other than its home area is called roaming. The price varies depending on your provider and the part of the world. While roaming is convenient, charges can be very expensive and are unlikely to be included in any plan you are on. You will be charged for receiving calls even if this is not the normal practice of your carrier in your country. Calls to your home country are international calls while roaming. A call made from the country you are roaming to will still be an international call to the person making the call and you will incur roaming charges for receiving it. Check rates with your home carrier beforehand, as you may unsuspectingly be making a $5/min phone call even from an adjacent country. Take care with voicemail and diversions. If your phone is on, you may incur roaming costs to receive an unanswered call, international costs to divert the call to home voicemail and international costs to retrieve the voicemail.

Consider using SMS (short messaging service) as a cheap alternative to making per-minute phone calls. These text messages can be sent between phones, with up to 160 characters per message (messages can nowadays be longer, but are still delivered and paid for in such chunks). While SMS messages can be more expensive when overseas (from $0.30 to $1.00 each), they are cheaper than international calls and can be very useful for keeping costs down. Sometimes receiving them can be free. Moreover, those who send you an SMS using a carrier back home will be charged at local rates.

Check to see if your home carrier has a sister carrier at your destination. For example, if you are a UK Vodafone user, check if your destination country has Vodafone as one of its carriers as there may be an affordable package for roaming within commonly-owned networks.

There are two things you have to check to ensure that roaming will work when you arrive:

1. Is your phone the correct type and can it communicate on the frequencies required by the foreign network?
2. Does your carrier have roaming agreements with the country you are visiting, and are you on a plan permitted to roam to another country?

Your phone

While roaming on your existing carrier lets you bring your home number with you, your phone must support the standards and frequencies of a network at your destination with which your carrier has a roaming agreement.

There is no need to unlock the handset or replace the SIM card, but if you're on the wrong frequencies or carry a CDMA-only handset into a country whose providers only support GSM, you will have no signal. Your home carrier should be able to tell you which networks are supported on your handset and plan.

Your carrier

Your carrier must have an agreement with a carrier at your destination to allow you to roam. Check that an agreement is in place and what frequencies the roaming carrier uses against the capabilities of your phone.

• GSM World - details on US and international roaming agreements
• Official EU roaming information page - for EU related information (tariffs, hints)

Check your plan allows international roaming. It may need to be enabled, which is must easier to accomplish before you leave home. Many pre-paid plans do not permit any form of international roaming, limit the networks that you can roam to or limit enabled services (such as SMS only).

Most phones default to a setting which automatically chooses a network for roaming. When in areas near the border of your home country, it may be worth trying to manually select your home network until you lose the signal. The farther away from the border, the weaker your home carrier's coverage; depending on terrain, there'll likely be nothing beyond 5 mi (8 km) from the border.

The foreign signal may actually be stronger also without crossing the border, especially in mountainous terrain, where the domestic signal is unreliable, where the signal path to the foreign tower is directly across water, as there are no terrestrial obstacles, and in backcountry, where no domestic towers are near. Mobile users in border regions like Niagara Falls, Windsor-Detroit or the Thousand Islands often disable roaming from the phone's menus to avoid being randomly hit with roaming charges on mobile telephones which never left their home country.

Rip-off networks

There are an increasing number of localized nano networks (especially in Europe) that may, unbeknownst to you, "capture" your mobile if you have set it to "automatic" network selection. For example, if you are travelling on a Stena line ferry the few miles between Scotland and Northern Ireland, the strongest signal is likely to be their own network with roaming charges of more than €1.50/min for incoming calls rather than the €0.05/min that the call would be capped at if you were still using an EU network. Cinemas have now got in on the act and are abusing what was once a socially useful technical advancement to stop phones ringing during performances.

At sea, out of contact with normal carriers, a ship-local network connected by satellite may truly be a service for those needing it, but the prices may be outrageous for those who could get by without – or when automatically switched to when land based networks are still in reach (even in the harbour).

Local and international SIM Cards

Mobile phone with battery removed, mini-SIM at the location where it is to be inserted.

Local pre-paid (sometimes known as "pay as you go") SIM cards are often a much cheaper alternative to roaming.

A SIM is a card which is inserted into an UMTS or GSM handset (often under the battery). It is necessary on GSM phones, where it provides the handset's identity as seen by the network. In CDMA handsets the functionality was integrated, but most now accept SIMs (or the R-UIM or CSIM variety).

The cards offer some memory for the phone's applications. E.g. your contacts may be either in the memory of the phone itself or on your SIM, unavailable if you change SIMs. Copy relevant info to the phone if possible, and to paper (interpreting the info may depend on features not available on the local SIM).

With a local SIM the phone – unless locked to the original carrier – is treated like a domestic one, with a local telephone number. Prepaid cards cost $10–50, depending on carrier; some include a small amount of prepaid airtime (typically no more than half the face value of the card).

No account setup, credit card numbers or bank accounts are necessary. In some countries, passports or IDs are necessary (to reduce use of phones by criminals); a handful restrict purchase of mobile numbers by non-residents.

To add credit to these SIM cards, buy "refill" (the common term in the US), "top up" (Singapore, the UK, Canada and New Zealand), "recharge" (Hong Kong and Australia), "reload" (Philippines) or "add value" cards/vouchers from news stands, telephone stores or convenience stores. ATM or online credit card top-ups may be possible with some providers. In some countries, credit (prepaid or plan) may be transferred between users of the same network by sending an SMS to the provider.

In some large international airports, outside security, mobile phone shops will offer a prepaid SIM without leaving the airport. A few vendors offer SIM cards intended specifically for visitors.

As a prepaid product, both the SIM card itself and the credits have limited lifespans. Unless periodically reloaded (usually with a code purchased from a local store or on a website with a local credit card) the SIM and the local telephone number will expire. As a general rule, lower top-up denominations tend to expire more quickly.

The card itself is packaged as a debit card-sized piece of plastic from which one can break out a smaller chip card in one of three sizes (mini SIM, micro SIM, nano SIM). The chip is the same, there's just less plastic frame around a SIM in the micro- or nano- size versions used by a few late-model Apple gadgets. Check which size your device expects before you buy.

A local SIM means one more number that needs to be distributed to your contacts; if you intend to visit many countries it may be easier to obtain a service which can be call-forwarded cheaply (such as a Voice over IP provider), distribute that number to your contacts and forward its calls to your local mobile phone/SIM when you enter a new country.

US-network SIM cards are sold by multiple vendors in Canada; Roam Mobility issues a T-Mobile prepaid SIM which can be activated for as little as one day a year, while Telgo.ca issues a similar AT&T prepaid SIM. These cost $3–5/day, depending on whether you want mobile data or just voice.

Another alternative is an "international card"; these usually allow free or cheap incoming calls in a significant number of countries and offer relatively cheap outgoing calls via an automatic callback service. Their phone numbers are usually based in the British Islands or Estonia. There are many different ones available, so shop around; the cards sold at airports may not be the cheapest. This avoids multiple changes of numbers.

Operators often make their websites very unhelpful and try to sell silly lotteries or games rather than offering clear information on their offer/costs, etc. The table below attempts to palliate this by centralizing the various alternatives available in every country. The rates below normally apply to standard rates that the providers charge you if you do not avail of a package or bundle.

Country	Operator	Plan/Card Name	Setup cost	Local Rate per minute	Data Rate per megabyte	Links with more information
France	Orange	Mobicarte	€7.90	€0.36/min	€5/week unlimited (throttling occurs above 100Mb)	Guide mobicarte (French)
France	SFR	La Carte	€10 in stores, €5 online	€0.55/min	€5/10 Mb/5 days with Wifi offer ?	Scroll down for a bunch of PDFs with some pricing information (French)
France	Bouygues Telecom	Carte	€10	?/min	€5/50 Mb/month	Bouygues Carte (French)
France	Virgin Mobile	Carte	€10	€20/2 hours + 100Mb of data or €30/3 hours + 200Mb of data	€5/Mb for excess	Cartes Prépayées (French) Fiche tarifaire (French)
France	Auchan Telecom	Le pack carte sim	€0 + €20 of communications	€0.40/min	€5/75 Mb/15 days	Auchan Telecom (French)
France	TopEnGo	All operators	N/A	N/A	N/A	TopEnGo, buy topups for every operator. Good way to assess relative value between operators (French)
France	UWT Mobile	Global SIM Card	N/A	€0.36/min	N/A	UWTMobile Global SIM Cards save up to 90% on your mobile roaming charges
UK	EE	Pay as you go SIM	N/A	30p	Data add-on purchase required	EE
UK	Vodafone	Pay as you go SIM	N/A	45p	£2/day for 50MB + 10p per MB in excess of 50MB	Vodafone Call Charges
Ireland	Vodafone	Pay as you go SIM	N/A	€0.45/min	€1.99/day for 100MB + 10p per MB in excess of 100MB	Vodafone Pay as you go Charges

SIMs and Unlocking

Android handset with slots for dual-standby SIM and microSD

If you want to use your own phone, you have to check (see above) that the phone can be used at your destination, type and communication frequencies and that it is unlocked (technically, "carrier SIM-locked".)

In some countries, providers may be required to provide subscribers with the unlock code for devices they own after a certain time period, usually for a fee. For many (but not all) common handsets, an "unlock" code may be purchased more cheaply from a wide selection of Internet vendors (typically $10-20); more rarely a handset needs to be taken to a specialized vendor to be unlocked.

Unlocking a phone (to allow access to competing mobile carriers) is not the same as "jailbreaking" (which allow access to non-Apple software downloads on Apple devices) or "rooting" (which provides a "run as administrator" option for Android programs). Some phones are easier to unlock than others. Older Nokia phones can be unlocked at home with a simple code, while Motorola or Sony Ericcson phones require additional equipment and may require you to bring your phone to someone. Some (Japanese domestic market phones) may use a different SIM-based method that attaches to your SIM, allowing you to take it from phone to phone. Shop around: unlocking services are generally cheaper and more easily available in Europe and Asia than in North America.

An alternative is to buy an unlocked phone. In some countries — for example China — phones are never locked. Various web sites and some shops in Western countries sell unlocked phones, usually at somewhat higher prices than the "deals" you can get by signing a contract for a service and taking a locked phone. Travel-specific capabilities like "quad-band", "dual SIM" or travel chargers, intended to keep handsets working on multiple carriers in multiple countries, are more likely to be available on factory-unlocked handsets from third-party electronics vendors. An unlocked 3G (UMTS/WCDMA) dual-SIM quad-band Android handset with no carrier-specific branding may cost anywhere from $150-500 from an online mail-order house, depending on brand name and capabilities.

While voice calls should work as soon as you install a subscribed SIM card and re-apply power to the handset, data typically requires various settings to be configured manually so that the handset can find the Internet gateway. For example, Rogers (Canada) provides this list of provider-specific settings:

APN: rogers-core-appl1.apn

MMSC: http://mms.gprs.rogers.com

MMS Proxy: mmsproxy.rogers.com

MMS Port: 80

APN Type: Default

APN Protocol: IPv4/IPv6

APN Roaming Protocol: IPv4/IPv6

The list of settings will be conveniently posted on the provider's web site, which you can't reach yet as you don't have mobile data set up properly. A few providers may also supply a username and password for mobile data. Carrier technical support is usually limited to providing a list of settings and advising you to ask your handset manufacturer. While MMS might only be needed for a specific few applications (usually, sending photos by text message), if you leave out the access point name (APN) you have no mobile data. Handsets purchased from individual providers usually preload the settings for that provider, but if you bring your own unlocked handset, you need to add your local SIM provider to the connection list for data. There may also be a setting to point the mobile browser to the new connection on the list, instead of your home carrier's gateway.

If your handset gives one-button access to voicemail, there is a number (listed in the configuration menu) which is auto-dialled by that feature. This number usually is read from the local SIM, but it's best to verify. Any on-screen "message waiting" indicators will only work for the currently-installed SIM, even if messages are waiting on your home provider (original SIM) and local provider (local SIM). Some handsets also use memory space on the SIM to store phonebook entries or wi-fi passwords; swap SIM cards and you may need to copy or re-enter this data.

Due to upgrades, many travellers have old handsets which are still functional. If this has the local frequencies, bring it; one handset keeps your existing home number active while the other takes advantage of reduced costs with a local SIM card. If a call arrives for your main number, call back from the local SIM at local prices instead of paying the higher fee for roaming.

Calls over Internet

Smartphones may be able to place voice-over-IP calls using a wireless Internet hotspot (or, with the right software, any decent Internet connection) by installing a softphone application and signing up to a VoIP provider. This is an inexpensive way to talk (unless your Internet fees are very high, which may be the case) and independent of the local cellular telephone networks, but is limited by the availability of Internet connectivity, and sometimes blocked at the Internet firewall.

Renting or purchasing a phone abroad

For greater flexibility, it might make sense to buy or rent an unlocked phone and prepaid SIM card at destination or prior to departure. With the local SIM you get the same rates that the locals pay and with a local phone or a phone bought specifically for use overseas, you are less likely to have compatibility problems with the SIM and local carriers.

You can often rent a local mobile phone, often even at the airport on arrival. However, in many countries purchasing a cheap phone and a pre-paid SIM will be more economical (even if used for just a week) as airport rental companies often charge much more per-minute than the local prepaid rates. Airport rental kiosks might be closed to travellers arriving on late night flights and have been known to run out of phones during popular events in high travel season.

In some destinations, providers market artificially-cheap prepaid handsets (in the US, "AT&T GoPhone" handsets start at $20 when the SIM alone is $10) but SIM-lock the handset to one provider which charges full price for the prepaid minutes. Unless the phone can be unlocked, it will not be usable with another carrier’s SIM card on your return and should be treated as disposable.

Especially in low-income countries or areas were theft and other types of crime are common a major advantage of getting a cheap "disposable" pre-paid phone, is that even if your phone is stolen you lose only the (relatively low) value of your phone and the remaining balance on the chip, and not the several hundred Euro a new model smart phone might have cost you.

That being said, if you intend to use a local phone and call local numbers, you might want to familiarize yourself with the local system and rates. In some countries those are not self-explanatory and you may find your balance "disappearing" after just a few days of not calling anybody or other shenanigans played on you by a dominant company, especially in countries with weak or no government regulations to prohibit such business practices.

Renting or purchasing a phone before departure

By having your phone before you go, you will have your phone number to give out to family, friends and co-workers. You will have a phone that is ready to use as soon as you land. Your handset will come with complete operating instructions in English, with information on how to check the remaining prepaid credit balance, how to add additional credit, how to contact customer service, and how to make and receive international calls.

Purchasing a USB charger

Mobile device makers, in response to EU pressure, have been migrating to +5V USB as a standard connection for recharging handsets. It should be relatively easy to find a USB charger compatible with local electrical systems at destination, or recharge from your laptop or any local computer. You will still need the cable connecting your phone to the USB contact on the charger (these are not fully standardized; most Android smartphones are microUSB, most Apple devices use a proprietary connector).

Information by country

Please see the Contact section of the destination country article for information on communications specific to one country.

North America

Frequencies in the Americas (ITU region 2, in blue) differ from the other continents

GSM (from the handful of major North American carriers that offer it) operates most often on 850 MHz/1900 MHz. AT&T and all three Canadian majors (Bell/Telus, Rogers) use 850 MHz/1900 MHz for their 3G (UMTS/WCDMA) networks. These are not the standard frequencies on other continents. Additional frequencies are used by new entrants, regional carriers or high-speed mobile data services.

AT&T and T-Mobile (USA) are GSM, as is Rogers (Canada). European handsets might roam onto these carriers (for a price, usually fairly steep) if they support local frequencies and the home carrier permits it. 3G (UMTS/WCDMA) is supported by more carriers than GSM, but frequency assignments vary widely. An unlocked quad-band GSM or UMTS handset should be able to take a local SIM at destination.

Many American carriers and resellers (Verizon, Sprint, Alltel, Tracfone, Virgin) make very heavy use of CDMA, an incompatible technology, with no GSM. In Canada, Bell and Telus were CDMA before 2009, but support 3G (UMTS/WCDMA) on all new handsets. Telus shut its CDMA sites down in 2015 and Bell will do so at the end of 2016. As CDMA-standard handsets are not required to provide removable SIM cards, a purchase of prepaid service from a US CDMA provider usually requires buying their branded handset.

Mobile subscribers in the USA and Canada must pay airtime for all calls, in or out. (This is not true in Caribbean nations.) Handsets are assigned local, geographic numbers; one may switch from wireline to wireless service and keep the same number. Calling to a mobile telephone therefore costs the same as calling to a landline. A handset taken out of its local home area incurs long-distance fees on incoming calls; this is less problematic on flat-rate plans. A prepaid SIM will not work until "activated" by phone or (with some providers) on-line, as the subscriber must choose a city (which need not be their place of residence) from which to obtain their local inbound number.

AT&T, Verizon, Sprint, T-Mobile (in the US) and Bell/Telus, Rogers (in Canada) operate national networks, so roaming is usually not an issue within the same country. Taking a Canadian handset into the US (or vice versa) can be an expensive ($1.50/minute) misadventure as, unlike the European Union, there is no legal limit to what providers can charge for roaming. Downloading large amounts of data abroad has cost some users hundreds of dollars or worse.

There are a few small regional carriers; these will incur roaming costs outside their home region and prepaid top-up cards are likely not in stores outside their home coverage area.

North American providers are notorious for flooding the market with branded handsets which are SIM-locked to one carrier on both pre-paid and post-paid services. A common tactic is to advertise an inexpensive (or even "free") handset in large print, while the fine print obligates the subscriber to a credit application for an expensive post-paid mobile subscription which takes years to pay off. Prepaid handsets are widely available at a reasonable initial price, but usually carry a higher per-minute rate and inflated prices for mobile data (a dime a megabyte on low-end Canadian prepaid handsets is not unusual). Most prepaid-cash plans do not permit roaming.

For travellers and infrequent users, prepaid is likely the only viable option. There is a confusing array of brand names; some are major carriers, some are "mobile virtual network operators" (which resell bandwidth on the network of a major carrier, at a lower price), some are merely one of the majors rebranded under another name to give the illusion of competition. Prepaid minutes from one brand won't work with the others, even if they're using the same underlying carrier.

Refills (in the US) or top-ups (in Canada) for prepaid cards are generally available at convenience stores, filling stations, big-box retailers, pharmacies and Canadian post offices. It is often possible to refill using a credit card online. Some store-brand virtual operators (such as Loblaws or Petro-Canada) sell through their own stores (selected locations) or online only. Long distance on basic low-end prepaid plans is expensive ($0.25/minute airtime + $0.25/minute or more for a trunk call is typical for the base "prepaid anytime" plans in Canada, while Internet telephony would cost a penny or two for the same call); it may be cheaper to use prepaid long-distance cards for anything more than a town or two away. Some higher plans, particularly in the US, include unmetered domestic long distance at no added per-minute cost or unmetered mobile airtime (often in off-peak hours). There are also extra-cost plans to extend the meagre data allotment on prepaid mobiles. Direct-dial overseas calls (or calls to former +1 809 points in the Caribbean) are expensive on prepaid plans and best avoided.

Billing for calls usually begins when the call is dialled, not when it's actually answered; providers also round call lengths up to the next full minute.

Directory assistance is available at 4-1-1 or +1-area code-555-1212 but is expensive; advertising-supported competitor 1-800-Free411 or websites like 411.ca, 411.info or canada411.com are cheaper alternatives. CAA/AAA automobile club members may obtain mobile roadside assistance by dialling *222 (*CAA or *AAA); some specific services like #TAXI (#8294) will hail the next available cab in much of Canada or the US for a cost of $1.25-$2.

In the US, few retailers sell used phones; independent phone shops which can unlock a phone are rare outside large-city immigrant communities. Factory-unlocked handsets, used handsets and codes to unlock existing handsets may be purchased online.

Prepaid GSM SIM cards are relatively difficult to find at US retailers. T-mobile offers one ($10) at their own shops or online, AT&T's GoPhone SIM is available (to US addresses only) by mail order on their website. Another option is buying the least expensive prepaid phone; if you intend to move the SIM card to your own unlocked handset, do not insert the SIM into the phone supplied as (on AT&T "GoPhone") that will lock the SIM into that phone.

Some online services will ship prepaid SIMs overseas or ship specialised "travel SIMs" to North American addresses, but typically overcharge badly (for example Telestial or Cellular Abroad).

Asia

• Some providers in China use TD-SCDMA (an incompatible alternative to W-CDMA on 3G UMTS handsets) or TD-LTE (as an alternative to LTE on 4G devices). These standards are rare in other countries.

• Japan and South Korea have no GSM coverage but have UMTS (3G) coverage, and most modern phones with 3G capability on the local frequencies should be able to roam there (Korea has 2G and 3G CDMA coverage as well as 3G UMTS coverage).

• Japan will not allow sale of SIM cards to foreigners on visa waiver or short term visas; in general, your options are roaming (with a compatible 3G GSM phone) or renting a phone. This can be done at the major airports (Narita, Kansai, probably others) or via delivery to your hotel or business. Expect to pay $1–2 (¥100-200) a day, plus fairly high per-call/per-minute rates.

• South Korea will only sell SIM cards to residents. Short term visitors will have to either use roaming or phone rental from an airport. Note that a South Korean resident is allowed to register a few SIMs, so you could use one registered by a friend,

• In Thailand, the best place to buy a used phone or get one unlocked is the 4th floor of the MBK mall in Bangkok. More than half the floor (nearly a full city block) is small mobile-phone vendors (most selling a mix of used and new), and many will do repairs, unlocks (and those that don't will generally be happy to take your phone to one that does and split the fee.) Expect to bargain hard!

• Visitors to Singapore can buy a sim card from currency exchange stalls, service centres of the TelCo providers or 7-11 convenience stores. However, they are required to give their passport at the point-of-sale for the service to be activated. A user is allowed to have a maximum 3 Singaporean sim cards registered to his name at a time.

Africa

• Egypt likewise won't let tourists buy SIM cards- as tourists would arrive, buy a card, then throw it out after a few weeks, proof of Egyptian citizenship is required to buy them. There is a way to rent cards, but it's a fairly arduous process involving contacting Egyptian phone companies before travelling, and so probably not worth it.

Australia/Oceania

• In Australia, 2G (GSM) is on 900 MHz (Optus, Vodafone, Telstra) with 3G usually on 900/2100 MHz (Telstra is 850/2100) and 4G displacing GSM on 1800 MHz. European-standard handsets should work seamlessly in 2G or 3G modes. Telstra will shut down its GSM in 2016; there is no CDMA.
• Virgin, TPG and Exetel are Australian virtual operators reselling bandwidth on Optus or Vodafone networks.

Europe

• When purchasing a prepaid French SIM card, activation is required. However the retailer does not require a copy of the passport from the user. Instead, the user will have to follow instructions that came with the French SIM card, which either instructs the user to log-on to the provider's website or contact a hotline. These can be purchased at retailers.
• Visitors to Italy are required to produce a passport when purchasing a SIM card in order to have the service activated. In some cases, a photocopy of the passport may be all that is sufficient - this is at the merchant/retailer's discretion. You can purchase prepaid SIM cards at foreign currency stalls and at stores of mobile phone providers.
• You can purchase UK prepaid (known here as "pay as you go") SIM cards at vending machines right before baggage claim in Heathrow Airport. Supermarkets and off-licence stores also sell SIM cards and top-up vouchers. Specialist mobile phone providers such as Lebara, Vectone and Lycamobile offer good rates for frequent overseas calls. At special events and public festivals, representatives of mobile phone providers give SIM cards out for free but you need to top up the required credit. Providers such as GiffGaff only operate online but their SIM cards can occasionally be found at certain events.
• Given the dispute over whether the Crimean Peninsula belongs to Russia or Ukraine, and given Russia's de facto control over the peninsula, most mobile phones that do not have a Russian SIM card will not work on the peninsula.

Satellite phones

Inmarsat satellite telephone deployed after the 2005 Sumatra earthquake in Indonesia.

In remote locations, without cell phone coverage, a satellite phone may be your only option. A satellite phone is not generally a replacement for a mobile phone, as you have to be outdoors with clear line of sight to the satellite to make a phone call. The service is frequently used by shipping, including pleasure craft, as well as expeditions who have remote data and voice needs. Your local telephone service provider should be able to give more information about connecting to this service.

The Thuraya network, using a Thuraya handset, allows roaming from GSM to Satellite depending on network availability.( Check to see if they have an agreement with your home network. Some networks (for example Vodafone UK) charge a very high rate for incoming calls (£6.00/min). If a lot of calls are to be made, buy a SIM card from a satellite phone provider. Calls on the Thuraya system cost from $0.50-$1.30/min. Thuraya network uses geostationary satellites over Europe, Africa, Asia and the Middle East, so check for coverage in the area you are travelling to. You may have to orient the antenna of the device towards the satellite for best reception.

The other consumer satellite telephony network is Globalstar. Globalstar's system in theory should be capable of worldwide coverage, but there are gaps in certain remote areas (such as areas of the South Pacific and the polar regions) where there are no gateway stations to link terrestrial telephone calls to the satellites. Cost is typically $1-1.50/minute plus a monthly subscription; in most countries, Globalstar issues numbers which look to be within the country (so a Canadian might get a Calgary or Smiths Falls geographic number) and its subscribers pay to receive calls.

For truly global walk-and-talk roaming, an Iridium handset (usually not made out of any quantity of the similar named platinum group metal) works anywhere with line-of-sight with the sky, on all land masses and oceans including both poles. Iridium uses a constellation of low-earth orbit satellites. Nominally, they orbit the Earth much like electrons orbit the iridium atom's nucleus, unlike Thuraya (or any system with geosynchronous satellites parked over the Equator, which can't see the polar regions). Expect to pay about USD 1.50-2.00/minute for outgoing calls, with only slightly lower rates to call another Iridium phone. Iridium does not sell direct and only sells phones through dealers who may also rent units as well.

For fixed installations in off-the-grid locations, satellite Internet may be adequate to allow Internet telephony. This is a standard way to reach points like Chicken, Alaska or an outfitter's camp in the distant wilds of Labrador; as no local infrastructure exists, a business offering a wi-fi hotspot by necessity feeds directly to a dish.

Satellite phones may be unavailable for purchase or illegal in Saudi Arabia, China, India, Myanmar (formerly Burma), Cuba, Iran, Libya, North Korea, North Sri Lanka, and Syria. Technically, they will still function in these areas. Some countries require a special permit for using satellite phones within their territory.

Conversely, the Newfoundland government will lend a satellite phone with very limited capability to travellers on the Trans-Labrador Highway through rural Labrador, where this is the only viable means to call for roadside assistance.

Usage

Most mobile phones come with a camera, and are useful for travel photography and video recording.