Ordered a 4s on my wife's account since it was her 3GS that was due for an upgrade. However, I'll be using the 4s and passing my 4 on to her. When the 4s arrives, I'll need to activate it, in order to activate the microsim in it and get her number off the 3GS sim and onto the microsim. Once her phone is active, can I just swap the microsims between the two phones to move the 4s to my phone number and the 4 to hers? Or do I need to somehow involve AT&T in this? Because I think AT&T is going to be very busy on Friday.