Request to unlock the device and contact the expert without providing a solution

Try Apples troubleshooting on the page. Worse case your device does not unlock best case your device does. 

FYI carriers won't know its unlocked until the token hits your device and it tells T-Mobile the device is unlocked.  What Apple means by carriers only being able to unlock is to make the request to unlock not actually unlocking it. You can't simply go to Apple to unlock it asking them to unlock it because they don't know if you still owe money among other things other than if the iPhone has been stolen.