So I sold my girlfriends 3g and my 3gs for $800. We both have upgrades so hopefully we get both new phones for $400. But anyways I am only 19 and dont have any credit yet so we have our phones under my moms account but we are the only 2 phones on the account and I pay the bill. I am buying the phones the day they come out. How would I go about doing this because its not my account?