Ok. Not sure if this applies to the other 2 carriers... But in the past, when you order an iPhone online, it arrives with a pre-installed SIM. The iPhone activation sequence for the new phone asks for billing info and already prompts you with the phone number attached to the upgrade. It will activate the SIM in the new iPhone and the old SIM will de-activate. But I am using another person's upgrade. So I have a few concerns. I don't want to activate the included SIM on the other person's line. I want to activate my number on it. I also don't want the other person's SIM (iPhone 4) to de-activate. Then I will have to go to AT&T and get 2 new SIM cards 1 nano (me) and 1 micro (them) to correct everything. Is the "first time activation" sequence tied to the iPhone itself (by Apple) and must be done with the other line? Or is it tied to the SIM card and can I call AT&T or Apple to change the activation sequence to activate my number? I am also worried that AT&T won't have extra nano SIMs lying around on Day 1.