You probably can't use your phone for travel if you have Sprint or Verizon anyway, since they don't use the same cellular standards as most of the world. And if you have a typical "tri-band" phone from another carrier you may be unable to use 3G data. It is unfortunately complicated in ways it does not need to be. And don't even get me started on the wonders of APNs when travelling...many customer service folks don't know how to set up data on foreign phones anyway. It should all be automatic.