At the moment no jailbreak tool works for iPhone 4S but a developer named Michael Capozzi has found a way out to unlock AT&T iPhone 4S without the help of any third party adapters like geveySIM.
Remember, its not a permanent unlock so you have to perform this unlock process whenever your iDevice will get restart.
Warning: We are not responsible for any loss so proceed at your own risk.
Unlock iPhone 4S on AT&T
- T-Mobile data plan
Insert AT&T SIM card
Dial 611 for AT&T customer service hotline and drop the call
From “Settings” menu on your iPhone, Turn ON “Airplane” mode
Remove AT&T SIM card and insert T-Mobile SIM card
Turn OFF WiFi and use “Forget this Network” option to make sure your device should not connect automatically to any network
Turn OFF Airplane mode and your iPhone will start search for network and it will display Apple splash screen
It asks for Activation and your iPhone will automatically get connected to EDGE network and you will find ‘E’ on top left corner of the screen
Wait for 20-30 seconds and then Turn OFF your iPhone
Turn ON your iPhone and again it displays Activation Required screen
When there will be only a single signal bar, tap on “Use Cellular Connection”
Eject SIM card
Activation Required screen will display again
Insert SIM card back
Enjoy, your AT&T GSM iPhone 4S is unlocked which can work over T-Mobile as well.