AT&T
As a GSM carrier, AT&T offers a comprehensive global network. You generally can roam from Canada down through Argentina; throughout Europe, Asia, and Australia; and in various African countries. Coverage is also available in Japan and South Korea, but you must have a phone that operates on the 3G band of 2100Mhz (you can rent one from AT&T). Coverage also extends to some cruise ships. AT&T sticks you with per-minute roaming charges, and you'll have to get your international roaming activated, but you're not liable for any long-distance charges. The carrier offers a selection of compatible phones, and if you manage to unlock your mobile, you can use a prepaid SIM card.

Frequent travelers can sign up for the AT&T World Traveler plan, which gives you a discount on most roaming rates in more than 195 countries for $5.99 per month. For travel closer to home, AT&T Canada offers a standard 59-cent-per-minute roaming rate for $3.99 per month, while AT&T Mexico offers the same rate for $4.99 per month. Customers with an iPhone, a BlackBerry or a Windows Mobile device have a few plans available; the cheapest gets you get 20MB of data in 65 countries for $29.99 per month.

* Varies by country and by international roaming plan.



The green areas indicate where you can use an AT&T world phone abroad. For a complete list of rates and coverage, visit AT&T's Web site.