AT&T won’t unlock your iPhone 4S, but this instructions might. Developer Daniel Scaleb found a bug in iOS 5 that allows you to unlock your AT&T iPhone 4S (GSM). This bug can unlock your iPhone 4S and use it on any other GSM carrier like T-Mobile here in the states. The best of this is that it doesn’t requires you to have the iPhone jailbroken, it’s done without any software or hardware modifications. Below is the 16 steps the developer posted in order to unlock the AT&T iPhone 4S; but first you’ll need a GSM iPhone 4S, an AT&T SIM card, and a T-Mobile Micro SIM which can be purchased from Amazon or directly from T-Mobile; you can also cut down your SIM if you currently have a standard non-micro SIM card.

  1. Insert original carrier AT&T SIM card
  2. Dial 611 for AT&T customer service hotline and drop the call
  3. Turn on Airplane Mode
  4. Take out AT&T SIM card
  5. Insert T-Mobile SIM card
  6. Make sure WiFi is off ( also tap on ‘Forget this Network” to make sure it doesn’t connect automatically later)
  7. Switch off Airplane Mode and iPhone will search for network. This is followed by the Apple splash screen appearing.
  8. Activation Required will be displayed on the screen
  9. EDGE network will activate automatically – notice the ‘E’ on the top left corner of the screen
  10. Wait for about 20-30 seconds and turn off the phone
  11. Turn on iPhone and the same Activation Required screen will be displayed
  12. When you see one signal bar, tap on Use Cellular Connection
  13. Eject SIM card
  14. Activation Required screen will be displayed the second time
  15. Insert SIM card
  16. Unlocked!
Scaleb stated that you must have a T-Mobile data plan for this to work. He also mentioned that this has a tiny chance of messing up cellular radio by doing this, but it’s very unlikely. All of this was done using a GSM iPhone 4S and it doesn’t work with CDMA iPhone 4S, according to the developer.
(via 9to5mac)