Ive heard some people say that it is not possible for an unlocked AT&T captivate to work on t-mobile because of the differences in UMTS bands. Vibrant: GSM 850/900/1800/1900 UMTS 2100/1700 Captivate: GSM 850/900/1800/1900 UMTS 2100/1900/850 My question to the experts though, is if I want to use nothing but voice and SMS / MMS on a prepaid sim with T-Mobile. Can I do this with the captivate? Seriously, the 3g means nothing to me and I have no desire to pay for it, would just like to use voice and SMS / MMS. Will this phone be able to do that at all?