I've been reading rumors that the iPhone 5S purchased from T-Mobile for full retail is actually *locked* and can only be unlocked after 40 days of using T-Mobile service. Can I get some confirmation on this? I'm sure tons of people preordered the 5S directly from T-Mobile last year, was it really locked? Is the consensus that purchasing the T-Mobile version from Apple gets you a truly UNLOCKED phone on day one? Thanks!