My provider is AT&T which up until recently was a CDMA mobile phone provider. Several years ago I obtained a SIM chip from AT&T to use in a GSM phone while in Europe. CDMA and GSM are incompatible. Calls to my US cellphone would automatically forward to my GSM phone in Europe. It was seamless, but not inexpensive and it meant carrying two phones (one for use upon arrival back in the US). Recently AT&T has been switching its service over to GSM in the US. Finally, the expanded AT&T GSM coverage in the US make it attractive to me for now I can use a single cellphone both in the US and Europe. The cellphone I use is a tri-band model meaning that it can send and receive on the frequencies used both in the US and in Europe. An ordinary US model GSM cellphone which is not tri-band will be unlikely to work in Europe. AT&T is not the only GSM provider in the US. There are others including Nextel.

Tom in Carlisle