iPhone on T-MobileA hacker has uncovered a bug in Apple's new iOS 5 firmware which allows certain iPhones locked to AT&T to be unlocked for use on T-Mobile. The hack works with the iPhone 3GS, the iPhone 4, and Apple's latest iPhone, the iPhone 4S. The biggest advantage to this trick is that you do not need to jailbreak your device or make any alterations to its hardware or software.

Instructions for performing the trick were posted to Pastebin yesterday, and later made big news on Twitter after they were tweeted by famous iOS jailbreaker Chronic. Those interested in performing the hack will need both AT&T and T-Mobile micro SIMs, and the 16-step tutorial we've pasted below. That sounds like a lot of steps, but don't be put off; the hack is actually incredibly easy.

Before we get into the how-to, however, let's just run through a few of the caveats. First, this trick will only work on GSM devices, so you won't be able to use it on iPhones built for CDMA carriers. Second, if you reset your device, you will need to perform the trick again to unlock it after a reboot.

Third, not everyone has found the hack to be successful, though many users have reported it works. Finally, and most importantly, there are reports that suggest "you could actually mess up your cellular radio doing this," though this is believed to be "very unlikely."

Brave enough to continue? Great! Then here you go:

  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!

See, that wasn't so difficult, was it? Did the trick work for you? Let us know in the comments down below.

[via 9to5Mac]