A bug has apparently been discovered in iOS 5 that allows a way to carrier unlock the AT&T version of the iPhone 4S, iPhone 4 and iPhone 3GS without the need to jailbreak or alter any hardware. The unlock will of course only allow you to use your iPhone on the T-Mobile network with Edge data speeds in the US however this is still a popular avenue for many iPhone users. If you want to try it, you will need a T-Mobile MicroSIM card or cut one down to the same size as a MicroSIM and follow the steps below:-

  • Insert original carrier AT&T SIM cardDial 611 for AT&T customer service hotline and drop the call
  • Turn on Airplane Mode
  • Take out AT&T SIM card
  • Insert T-Mobile SIM card
  • Make sure WiFi is off ( also tap on ‘Forget this Network” to make sure it doesn’t connect automatically later)
  • Switch off Airplane Mode and iPhone will search for network. This is followed by the Apple splash screen appearing.
  • Activation Required will be displayed on the screen
  • EDGE network will activate automatically – notice the ‘E’ on the top left corner of the screen
  • Wait for about 20-30 seconds and turn off the phone
  • Turn on iPhone and the same Activation Required screen will be displayed
  • When you see one signal bar, tap on Use Cellular Connection
  • Eject SIM card
  • Activation Required screen will be displayed the second time
  • Insert SIM card
  • Unlocked!

We haven’t tested the unlock ourselves but a lot of others have and claim that it is definitely a working unlock solution for the iPhone 4S, iPhone 4 and iPhone 3GS. Unfortunately it will not survive a reboot of your iPhone; if you do that, you will need to repeat the steps above. If you give this a try, let us know if you have any success!

Source: 9to5Mac, @Chronic, Danielscalab.com