My girlfriend has mentioned getting me an iPhone 5 as a Christmas present, but my line is not eligible for an upgrade until next March. We share a plan and her line is eligible for an upgrade, however. I know it's possible to swap the phone between lines post purchase, but my question is: Is it possible to get the eligibility swapped to my line before the phone is purchased? I'd like to, if possible, activate the phone on Christmas day - I'm assuming AT&T's customer service reps would be off that day.