im Really pissed, i bought an UNLOCKED iPhone 7 from Best Buy with a PREPAID T-Mobile sim. I was under the Impression that I could switch carriers at any time. I switch my number to AT&T and ordered a new sim and unfortunately that same does not work in my phone. T-Mobile refuses to unlock my sim and Apple has been no help either. They told me to factory reset and insert the new sim and that crap hasn’t work it’s still locked to T-Mobile. I have pre-paid and an unlocked phone for the freedom and flexibility and T-Mobile sucks.
Best answer by gramps28
Actually it's Apple that sucks since it's their policy.
It's called the Apple Reseller Flex policy.
Apple sells their phones as unlocked to Best Buy and other 3rd party store but
when the first sim card is inserted into the phone it will lock to that carrier.
If you used an AT&T sim first you would be in the same boat.