http://www.apple.com/iphone/LTE/ I plan to use this in China and A1524 comes with China's LTE band. T-Mobile, Verizon and ATT version doesn't support China's LTE band. It seems like 6+ model: A1524 has all the LTE band that A1522 GSM version plus more. And only C Spire, Sprint & US Cellular has A1524. Can I buy from Sprint outright, paying full unlocked price without signing into contract? Are Sprint iPhones always unlocked?