Global Cell Service

Using a prepaid cell phone while abroad

Cellular companies in the U.S. use a number of proprietary networks for their cell phone service, and that means that a cell phone made to work with Verizon's CDMA (or Code Division Multiple Access) network will not work on a GSM (or Global System for Mobile communication) network such as those supported by T-Mobile and AT&T. This could be important if you travel overseas and would like to take your cell phone with you, since most European, African and Asian cell phones work on GSM networks. Be aware that American GSM phones and foreign GSM phones work on different frequencies, so you will need a specific tri- or quad-band world phone with multiple frequencies.

In order to swap SIM cards, you will have to ask your cell phone service carrier to unlock your phone, allowing your phone to send signals on a different frequency. Some carriers will let customers have unlock codes as soon as 90 days into a contract, but others do so only reluctantly. Websites like Unlock123.com will unlock Nokia phones for free (for phones that can be unlocked with a code) or $23 (for phones that need a new SIM card). TheTravelInsider.info will do the same thing for most Nokia phones along with many other GSM phones, including models from Samsung, Siemens, Sony Ericsson, Motorola, LG, BlackBerry and Treo, as well as the Apple iPhone. Prices range from $5 to $30. The 2006 Digital Millennium Copyright Act has made it legal for individuals to unlock cell phones for personal use.

The advantage of switching SIM cards is that a local SIM card gives you a local phone number, making in-country calls inexpensive (avoiding very high roaming fees). In addition, most countries don't charge you for incoming calls. CNET warns that voicemail messages can cost more than at home, though.

Most U.S. prepaid wireless carriers will also let you provide your own phone, as long as it's unlocked and supports their network. So if you already have a GSM phone, you could buy minutes from T-Mobile Prepaid, for example. Carriers may charge an activation fee if you don't buy one of their phones, however.

Most prepaid wireless carriers will let you make calls overseas, but international calls often cost more. Virgin Mobile, TracFone and all of the major carriers (including Verizon, AT&T and T-Mobile) support international calls, but rates are sometimes high. However, Straight Talk prepaid wireless works only within the United States. Your best bet is to check before you travel.