Hi, I live in europe and now i'm in the US an i want to buy iPhone 5. I want the A1429 model (Verizon / Sprint) unlocked as it has support for LTE in europe. Is it SAFE to buy from an apple store a Verizon/Sprint phone without contract and count on it being Unlocked FOREVER? [Is it more safe to buy an ATT iPhone 5 without contract and give up for LTE?] Thanks!!