I have an iPhone 4S that is not eligible for upgrade. My wife has a 4 that is eligible. When I ordered the 4S it came with the Sim card preloaded. My question is if I order a 5 with my wife's upgrade eligibility, will I still be able to transfer my number to the 5 or will there be a som card issue that will not allow this? I guess the question is are the Sim cards interchangeable between the 4S and the 5?