Thereare some problems with using a US cell phone abroad and most of thepeople prefer other services because of this. First of all, it is anissue that to make phone calls on your US cell phone outside the US,especially overseas, you must generally have a GSM (Global System forMobile Communications) phone, which will work on international bands.making phone calls overseas on your GSM cell phone contracted with aUS company can be done If you've got a GSM phone may be horrendouslyexpensive because you're roaming, basically. In order to avoid suchas situation, you must have an unlocked GSM phone so you can buy SIMcards (subscriber information module chips) for it. As you know well,SIM cards enabling you to make phone calls in the country you're inare available on practically every corner in some of those countries.But still there is a problem reported by people such that you can'talways put those SIM cards in your locked US phone, GSM or not.People assume that it is because most US cell companies lock theirphones so that you must sign over your first born and swearallegiance to the company before they'll hand over a not-so-freephone, which means you can't switch your love to any other companymid-contract without then sometimes having to buy the phone. Buying a[Only registered and activated users can see links. ] can be easy anywhere in the country you are visiting but stillyou will have to face these kinds of problems.