so basically this is what I'm going to do... my mom's friend is gonna buy ME an iPhone 4 (cause my mom is currently a Sprint user and I'm living in brazil). He's already an Att user and he's gonna sign a new 2 year contract and pay $400 on the iPhone, but, to activate the phone you need a MICRO SIM, he's transferring his number temporally to the MICRO SIM, after activating the phone he's gonna transfer his number back to the OLD SIM, and give me the phone with the micro SIM so that I can activate whenever I have to. IS HE ALLOWED TO DO THAT? (transfer his number to another SIM, and back to the old SIM in that amount of time)