My replacement iPhone 5 arrived and I need to activate it. I don't know how to do it. I thought by syncing it up to iTunes, it would detect my settings, but I guess I have to contact AT&T to deactivate my first iPhone 5? Does it have to do with my SIM Card? Can I just swap the cards? There were no instructions and I want to figure this out before I ship the original iPhone 5 back to Apple. Any help would be much appreciated! Thanks!