FAQ: Swapping SIMs to save big on calls abroad

For travelers who can't stomach the high rates U.S. carriers charge for international roaming, there is an alternative.

Marguerite Reardon Former senior reporter
Marguerite Reardon started as a CNET News reporter in 2004, covering cellphone services, broadband, citywide Wi-Fi, the Net neutrality debate and the consolidation of the phone companies.
Marguerite Reardon
12 min read

For travelers on a budget, slipping in a new SIM card may be the best way to ensure they won't break the bank while using their cell phones on a trip abroad.

U.S. carriers, such as AT&T and Verizon Wireless, have been trying to make it easier and less expensive for mobile subscribers to use their cell phones when traveling in another country. And indeed they have. All the major carriers offer phones that can be used for international roaming. And some have even added special international packages with reduced calling and data rates to encourage travelers to keep their cell phones on while they're on the go in a foreign country.

But for U.S. cell phone subscribers, who are used to free local and long-distance calling, as well as, free domestic roaming and big buckets of voice minutes and text messages, these "reduced" rates don't look so cheap.

But there are alternatives, especially for people who have unlocked GSM (Global System for Mobile Communications) phones. By simply replacing the existing SIM (subscriber identity module) card in the back of their phones with SIM cards from local operators or ones designed specifically for international roaming, cell phone users can save up to 80 percent when making calls instead of using a U.S. carrier's international roaming plan.

The proliferation of inexpensive prepaid cell phone services throughout the world has made this practice simple. But using a local or international roaming SIM often requires planning and a little legwork, which means it's not for everyone. Still, the savings may be just too big to pass up.

To help readers figure out exactly how all this SIM-card swapping works and to help them determine if it's the right solution for them, I've put together this FAQ to answer some of the most basic questions. If I've missed any important information, feel free to e-mail me and/or share your thoughts with other readers in the Talk Back section below.

Let's start with the basics. What is a SIM card?
A SIM card is a postage-stamp-sized chip, which is essentially the brains of the phone, that slides into the back of your phone, usually underneath the battery. Changing SIM cards is very easy.

If I replace my SIM with a different SIM from another country, will I be able to use my U.S. phone number or check my U.S. voice mail from my phone?
With most prepaid SIM cards, the answer is no. You will get a new phone number that is local to the country where you bought the SIM. Depending on the country and the service you have, you may have access to voice mail. But some wireless operators in some countries don't offer it for prepaid users.

One company I found during my research, Brightroam, offers customers the ability to forward their North American cell phone calls to their international cell phone numbers. Brightroam charges users about 69 cents a minute to accept these calls.

Where can I get a prepaid SIM card?
There are a few options. You can buy a prepaid SIM card for the specific country where you are traveling either online before you leave for your trip, or you can buy one from a local wireless carrier when you get to your destination. Buying a prepaid SIM in the U.S. will likely cost you a little bit more because companies often tack on a surcharge. For example, if you are going to the U.K. and you bought a prepaid SIM card online from a site such as Telestial, it will cost you about $29 for the SIM card. This will give you a little bit of airtime, between $1 and $7, depending on the service provider you choose.

Often it's cheaper to buy a SIM when you get to your destination. For example, using Orange in the U.K., you can get a SIM card for less than $15, which should also come with some airtime.

The other option is to buy an international roaming SIM card, which you can also purchase online from several different companies, including Telestial, Mobal, and Brightroam, to name a few. The benefit of these SIM cards is that they allow you to make inexpensive calls in almost any country you travel to.

SIM cards bought for a specific country often have high roaming rates when these SIM cards are used outside that country. Telestial, which offers low-cost roaming in over 130 countries, offers a unique international roaming SIM that offers users two numbers: one from the U.K. and one from the U.S. Users will receive calls and text messages when people call either number. Calling rates start as low as 29 cents a minute. The SIM card itself costs $29 and comes with $10 of airtime preloaded.

How much can I save using a prepaid or international SIM card instead of using my carrier's international service?
If you are on a tight budget and you don't mind leaving your regular cell phone number at home, prepaid SIM cards are really the cheapest option. I'll use the U.K. option as an example.

Using AT&T's service in the U.K. , you would be charged $1.29 a minute for all calls made while in the U.K. With the special discounted World Traveler package, which costs $5 extra a month, the international roaming rate would be 99 cents a minute. Text messages are 50 cents to send and picture messages are $1.30 each.

Compare this to swapping your SIM card for an international roaming SIM card from Telestial. With this card, calls to landline phones from the U.K. to landlines in almost any other Western European country as well as the U.S. and Canada will cost 29 cents a minute. It will cost 69 cents to make calls to a U.K., Western European, U.S., or Canadian cell phone number. Calls to Telestial voice mail and customer support are free. All incoming calls are 29 cents a minute, and sending a text message will cost 69 cents. Receiving text messages is free.

Calling rates for country-specific SIM cards are even cheaper. With a country-specific SIM card ordered from Telestial online, all incoming calls are free. For calls made to landlines and cell phones in the U.K., you can expect to pay about 30 cents a minute. Text messages will cost about 20 cents each to send and receive. And calls to the U.S. and Canada are about 8 cents to landlines and 12 cents to cell phones.

Buying a SIM card when you get to London from a local operator, such as Orange, can offer even better deals. Orange offers a variety of service options for prepaid customers. In general, domestic calls range from 30 cents to 40 cents a minute, depending on the exchange rate. (All calls are billed in local currency.) And texts are about 20 cents to send and receive. With a special international plan, customers can also make international calls for as low as 10 cents a minute. Orange also offers free text messaging for customers when they "top up" or add money to their phones. One plan offers 300 free text messages with a 10-pound top up. And you can get 600 free text messages with a 20-pound top up and a 30-pound top up gets you unlimited text messages until the card expires.

Do SIM cards work in any phone?
No they don't. They only work in GSM phones. And the phones must be unlocked. If you live in the U.S., phones from AT&T and T-Mobile USA operate on a GSM network and can be unlocked. You can call your carrier to ask for an unlock code, go online to pay a fee for the unlock code, or go to a cell phone specialty shop and pay to have them unlock your phone. Verizon Wireless and Sprint Nextel do not operate using GSM, so most of their phones don't use SIM cards, and therefore cannot be unlocked. But these operators also offer a select set of world phones, which use GSM. These phones can be unlocked just like any other GSM phone, and a new SIM card can be slotted into them. Check the Verizon and Sprint Web sites for a list of GSM-compatible phones.

Can I buy an unlocked phone before I leave for my trip?
Many Web sites, including Amazon.com through various partner retailers, sell unlocked GSM cell phones. Also big phone manufacturers, such as Nokia and Sony Ericsson, sell unlocked GSM phones in their stores and online. But before you buy an unlocked phone or plan to use your own unlocked phone abroad check to make sure that the phone supports the appropriate radio frequencies. In the U.S., GSM operators use the 850MHz and 1900MHz frequency bands. In Europe they use the 900MHz and 1800MHz frequency bands. So it is important to make sure the phone you buy or plan to use on your trip operates in the right frequency.

Can I buy an unlocked phone abroad?
Yes, many wireless operators around the world offer inexpensive prepaid phones. For example, Orange in the U.K. sells the Samsung E1120, a very basic phone, for about $15. If you plan on using the phone you buy on future trips, make sure it is a quadband phone that supports all the major GSM frequencies used around the world.

If I don't have an unlocked GSM phone can I rent one?
Yes you can. Several international travel Web sites offer phone rentals. For example, Telestial rents phones starting at $7 a day for trips that last between one and five days. The longer your trip, the lower the per-day rate will be. And for trips more than 46 days long, the company rents phones for $2 a day.

Sometimes you are also able to rent phones at the airport. But if you need to rent a phone, it's best to check ahead of time that it is available or order one online before your trip.

Ok, so now that I have an unlocked GSM quadband cell phone, should I get a local SIM card or one of these international roaming cards? What's the difference?
Whether you use a local SIM card or an international roaming SIM card depends on a few factors. Are you planning to stay in one country on your trip or will you be traveling to multiple countries? Do you plan on traveling to other countries in the future? Do you expect to return to the same country you're traveling to on this trip?

The general rule of thumb is that if you are planning to stay in one country during your entire trip or you plan on returning to that same country often, then a local SIM might be the best solution for you. But if you plan to go to more than one country during your trip or if you are a frequent international traveler to different destinations, then an international SIM might be a good fit for you.

So what are the pros and cons of the local SIM card?
Pros: Local SIM cards offer the best rate for local calls. You will have a local phone number in the country in which you are traveling, which will make it inexpensive for local people to call you.

Cons: If you don't order one online, you have to spend precious vacation time and effort looking for a store to buy a SIM card. The instructions and prompts to set up and use the service are in the local language. So if you only speak English, and you are traveling to Italy, for example, this could be problematic. Calling internationally to the U.S. or Canada may be cheaper than what your home wireless operator charges, but the rates could be higher than rates offered for international roaming SIM cards, which are designed for tourists. Roaming outside the country where the SIM is supposed to be used might not be available. And if it is available, it is likely to be expensive.

What are the pros and cons of using an International roaming SIM card?
Pros: Calls to the U.S. are often cheaper than any other cell phone calling plan. You can order the card online and get your international phone number before you leave on your trip, so that you can give it to friends and family. Because you have the card in advance, you won't have to waste time looking for a place to buy your SIM card. You can keep your international SIM card and phone number and use it on future trips. For example, Telestial allows you to reactivate your phone number even if you haven't used it in a long time. Instructions, prompts, and customer support are in English.

Cons: Making calls and sending text messages will be more expensive than using a local SIM card. You will likely have a cell phone number that is based in a country where you are not traveling. Telestial's numbers are from the U.K. This means that locals, outside the U.K., will be charged an international rate when calling your number.

Can I reuse my SIM card for future travel?
Most prepaid SIM cards have expiration dates. If the SIM card is inactive for a certain period, usually about three months, users will lose whatever money they have put on the card and haven't yet used. After about nine months to one year, many operators will deactivate the SIM card and phone number. This means that if you return to that country after this time, you'll have to get a new SIM card.

How can I add money to my prepaid SIM card?
There are often several ways to "top up" your phone. You can get prepaid cards at convenience stores, tobacco shops, or from the carrier's retail store. Some operators allow money to be added via a Web site or by calling a special number. Some services also will automatically top up your account using your credit card if your account falls below a certain limit.

What about data? Can I get prepaid services that offer 2G or 3G data services for surfing the mobile Web and checking e-mail?
It depends on the local carrier and the SIM card you are using. Some operators offer access for mobile Web surfing using WAP (Wireless Application Protocol) with their SIM cards. If that is the case, you will be able to surf the mobile Web and check Web-based e-mail. But some prepaid SIM cards don't offer any data service, so check before you buy. If you want 3G service for a smartphone, you must also ask for that. Some carriers offer it, and some do not.

Some international roaming SIM cards, such as the Passport products from Telestial, do offer data services. The Telestial service offers GPRS (general packet radio service) data service in 71 countries and 3G service in 10 countries. Your phone must be able to handle data services, and it also must be configured to work with the prepaid data service. The company offers instructions for doing this for different handsets on its Web site.

Rates vary depending on the country where you are using the service and they are also based upon kilobytes used. For example, using Telestial's service downloading 1MB of data costs $5 in the U.K and Ireland. And the rates go as high as $30 a megabyte in Chile and Australia.

What about push e-mail for my BlackBerry?
BlackBerry data services generally do not function using a SIM card from a foreign carrier. The service is usually tied to your existing post-paid service in your home country. That said, a SIM card in an unlocked BlackBerry will give you access to voice, text messaging, and in some cases Web browsing. So you can check your e-mail via a mobile Web browser or through specific applications loaded onto your phone.

There is at least one company called Brightroam that offers a BlackBerry SIM for $30.99. The company's Web site says it offers BlackBerry data services for $1.50 per kilobyte. The Web site also sells new and refurbished unlocked phones.

Here are a few additional tips for buying and using SIM cards overseas:
•  Be prepared to provide some personal information, such as passport number and a local address if you buy a local SIM card from a carrier in the country you are visiting. In the past prepaid phones have been used by terrorists to communicate with one another and also to detonate bombs. So in many countries, especially in Europe, local carriers are requiring customers to register for prepaid cards. And some countries won't allow nonresidents to purchase prepaid phones or SIM cards, so check ahead of time.

•  If planning to buy a SIM card or prepaid phone locally, go to a local carrier's Web site in advance and locate stores where are. This could save you time and effort looking for a store once you get there.

•  Leave your international phone number on your outgoing voice mail on your home cell phone. This way friends, family, and colleagues know how to reach you.

•  Take the number to check your voice mail remotely with you, so you can call and check your home messages while you are away.

•  Don't forget an adapter for your phone charger.

Are there other options for making low-cost phone calls while traveling?
Yes. Wi-Fi is a great way to check e-mail or make cheap phone calls using services like Skype. But you must have a phone that has Wi-Fi built in. And you must be in a Wi-Fi hot spot. Skype uses the Internet to allow people to make free or very inexpensive calls to anywhere in the world. When using Skype in a hot spot, all calls to other Skype users are free. And calls to cell phones and landline phones can be made at very inexpensive rates.