Thinking of going to walmart & purchasing a pre-paid at&t phone & using that line to upgrade to the iphone 5 &n then once i receive it in the mail, just transfer the phone to my number on the account. Is this possible? Pretty sure i'd have to visit an at&t store to do the nano-sim swap but my question is would i be eligible for the fully discounted pricing if i upgrade the prepaid line? i'd hate to go out and purchase a pre-paid for nothing.