Unlocking device iPhone 5 returns error: We're sorry. We can't unlock this device.
I have an iPhone 5 that is paid off and still active on AT&T. I want to unlock it so that I can move the SIM card to a newer phone and sell the iPhone 5.
When I enter information in https://www.att.com/deviceunlock/ , it identifies the IMEI number as Apple iPhone 5 Model A1428.
When I press the submit button, I receive the error message: "We're sorry. We can't unlock this device."
How do I unlock the phone 5?
Maybe this iPhone 5 is unlocked already. How can I tell?