compatibility issues with AT&T or T-mobile sim card

I am not sure if Arduino GSM Shield is compatible with the technologies of our local service providers , like AT&T or T-mobile, as it does not use EDGE or UMTS technologies to send data. The link for the list of cell phone service providers technologies is http://en.wikipedia.org/wiki/List_of_United_States_wireless_communications_service_providers Someone please confirm me if I will be able to use Arduino GSM Shield to work with local cell phone service providers,i.e AT&T or T-mobile

thanks a lot in advance

siddhartha

Arduino GSM Shield is compatible only with GSM operators. Not CDMA, UMTS and other types.