Looks like you haven't paid off your device yet
Whan I try to unlock as non-customer, I have this message:
Looks like you haven't paid off your device yet. Follow these steps to pay off your installment plan. Then, wait 48 hours before you submit a new request.
I am not resident of US and don't have at&t account. How can I unlock my iPhone 6S Plus for international use with different carriers?