How to Beat the High Costs of Dialing Abroad — Practical Traveler - NYTimes.com

Michelle Higgins

"First, ask your carrier if your phone can be unlocked. Customers of AT&T and T-Mobile will have the best luck with this because their signals are compatible with more foreign carriers. Most cellphones that operate on Verizon and Sprint aren’t compatible with networks outside the United States, making unlocking beside the point. If you use one of those carriers, decide whether it’s better to pay the carrier’s roaming rates and simply limit calls or buy a basic, unlocked phone for calls and texts (which can usually be found for $40 or so) in the country you’re visiting."