What happens after one pays in full from any of the 4 carriers? Can I immediately switch to a different carrier or not have any phone plan from any carrier from the day one? Or do I get tied down to the selected carrier for a certain period of time (maybe 1-3 months?) and its phone plan before I can drop the phone plan, have it completely unlocked and go rogue? Not that I will buy iphone 6s to have a unlocked Wi-Fi super mini ipad, but for the argument sake, let's say that's what I want in the beginning. Meaning no cellular plan + completely unlocked to be able to purchase any pre-paid plan from any carrier (as long as its band is supported) from the day one and for however long and often as I want. I'd assume that since I pay the full upfront, should I choose, I should be able to do this from day one. And choosing one of the 4 carriers at apple store to buy is just to choose GSM or CDMA model, a mere formality. But I get the sense that I may be being naive and there may be a bit more red tapes, no matter what carrier I choose? Also I get the sense that level of ease of doing this may be different from the 4 carriers. In other words, the level of ease would be T-mobile>AT&T>Verizon>Sprint. But I feel like even with T-mobile, supposedly the easiest, I might be forced to purchase their cellular plan initially for a short period of time before I can request to have it unlocked and drop its plan. And possibly worse with other carriers. Am I wrong here? Let me know.