I currently have a 2012 iPhone 5 that has an AT&T SIM card. Unfortunately, the plastic case for my iPhone is almost impossibly hard to remove, so I cannot remove the SIM. I don't want to break the case off. So now I want to buy a new SIM-free iPhone 6s. Some questions: 1. If I got to an AT&T store, will they give me a new SIM card? 2. When I activate the new SIM card with a new iPhone 6s, will the SIM card on my iPhone 5 automatically be deactivated? 3. Is there a reason I should prefer the AT&T "pay in full" iPhone (which presumably comes with a SIM card) over the SIM-free iPhone 6s?