I own a samsung captivate from my AT@T contract but i don't want to renew my contract. I would much rather use one of the prepaid plans. Can i just put a go phone sim card in my captivate and go, or do i have to go to an AT@T store so they can do it? Is it even poosible to use a captivate on a prepaid AT@T plan? Thanks for all the help in advance.