A strange bug on iOS 5 has apparently been found by Michael Capozzi (via Chronic) that allows the carrier unlock of the AT&T version of the iPhone 4S, iPhone 4 and iPhone 3GS without any software or hardware tweaking.

The unlock reportedly allows you to use your iPhone on the T-Mobile's network with Edge data speeds in the U.S. as long as you have a T-Mobile SIM card.

To get started, you will need to cut the T-Mobile SIM card so that it fits into the Micro-SIM card slot in the iPhone 4S.

Many people claimed they have exploited this bug and have successfully unlock their AT&T iPhone 4S for use with the T-Mobile carrier while others said that it's not working for them, Gizmodo reported.

Although the method appears to work, it has not been tested by the tech experts at the IBTimes. If you want to unlock your device on the iOS 5 firmware by exploiting the bug, follow the directions below:

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!

Check out the video here:

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