> Verizon, for example, says in its FAQs that all smartphones the comms giant or any of its retail partners sells are locked for at least 60 days from purchase,

> Verizon, for example, says in its FAQs that all smartphones the comms giant or any of its retail partners sells are locked for at least 60 days from purchase, even when you've paid full retail price or paid off your device payment agreement early. It claims the policy helps to "prevent theft and protect customers from fraud." Further, as noted by multiple commenters (and this can be confirmed by a google search turning up numerous accounts): T-Mobile automatically locks an unlocked device when you insert an AT&T sim into it.