I'm giving my son an early generation iPhone as a gift. I want to unlock/jailbreak before giving it to him so it's ready to go. My question is, can I use my SIM card from already unlocked iPhone, or do I need to have the SIM card from his current T-Mobile phone to unlock. I presume I can use mine to unlock since we both have T-Mobile SIMs. It will be alot easier to surprise him If I don't go fish around for his SIM card while he's asleep.