Had ATT unlock phone. They informed in instructions to connect phone to itunes and back up and restore phone. After restore phone will be unlocked.
Instructions also indicate to sims card installed. Would the sims card be the old one from ATT or the new carriers sim?
iPhone 4, iOS 6.1.3
Start with the AT&T sim.
Made a Backup from your iPhone, in iCloud it's the best way.
Then put the sim from another provider, if works your iPhone its Unlock.
While I agree with your recommendation of a backup they first need to Restore their iPhone as new in iTunes prior to trying the other microSIM. I agree with imobi, start with the AT&T microSIM.
i started with the AT&T sim - when i did the restore i got a message
Congratulations Your iPhone has been unlocked - i then put in a Tmobile sim and it worked
also its a good idea to power the phone off before switching sim cards
I had Iphone 4 unlocked by ATT. Instructions say to connect to itunes to backup and restore phone. Sims card to be installed at time of backup and restore. Should it be ATT sims or new carrier
