A great news comes from an iOS developer which comes public on the internet, a bug which is capable to unlock your iPhone 4S device to be compatible with any carrier without jailbreak.
Also, this bug works is not available only for iPhone 4S but also works for iPhone 4 and 3GS.
For unlock your iPhone 4S, 4 or 3GS is simple, just follow the below steps in order.
- Insert original carrier AT&T SIM card
- Dial 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
Below you can watch a video demonstration.