I have a couple of iPhone 4s that I purchased for myself and a family member. Said family member has decided that they would like a simpler, more basic phone (no data, etc.), which is fair enough given that they really only use the phone. My question is, rather than return the iPhone 4 to the store, can I resell it (keeping the sim card), and purchase an AT&T compatible phone from ebay, or elsewhere to utilize their phone number? I realize that the new sim cards would not fit, but a call to AT&T would remedy this with a new sim without buying a different contract etc. right? Thanks in advance.