I contacted AT&T and followed their directions, but I don't know if it worked.
Posted on Oct 4, 2014 1:22 PM
Q: How do I tell if my iPhone 5 is unlocked without using another sim card?
Connect the phone to iTunes on your computer, click on its name, and click the button to Restore iOS. If the phone is unlocked iTunes will finish the restore, then display
A bit of background to the process
iPhone: About unlocking