FAQ

You can unlock your phone by submitting an unlock request to the network operator you bought your phone and plan from. Note that your network operator will only approve your unlock request if all contractual and financial obligations have been met. If not, you will have to pay a termination fee. 
One way to find out whether you have a locked phone is to look for notifications like “blocked,” “barred,” “incorrect SIM,” or “SP lock.” If you see any of these messages, get in touch with your network operator as soon as possible.