There has been a significant breakthrough in the iPhone 4S unlock dilemma. A rather strange bug will allow you to unlock GSM iPhone 4S baseband 1.0.11 on iOS 5 firmware without having to jailbreak. Detailed instructions on how to do that given after the jump.
The bug was initially found by Twitter user @xoicos who claims that similar result can also be achieved on a CDMA iPhone 4S however the procedure for that is a little different from that of GSM iPhone 4S unlock.
As you would already know by now, there is no jailbreak for iPhone 4S. Since there is no jailbreak, there is no software unlock for iPhone 4S. Developers are working hard on developing a jailbreak for iPhone 4S and they have even demoed iPhone 4S jailbreak on video. It will still take a lot of work before an iPhone 4S untethered or tethered jailbreak is possible. Until a jailbreak is developed, there won't be a software unlock for iPhone 4S. Thankfully, the procedure that we've mentioned below will unlock GSM iPhone 4S baseband 1.0.11. FYI: You can also buy a factory unlocked iPhone 4S from Apple. This procedure will allow you to unlock your AT&T iPhone 4S so that it can be used with T-Mobile USA or other compatible GSM networks around the globe.
How To Unlock GSM iPhone 4S Baseband 1.0.11:
Step 1: Insert the AT&T micro-SIM in iPhone 4S
Step 2: Call AT&T customer service by dialling 611. End the call as soon as it starts ringing
Step 3: Now toggle Airplane Mode ON
Step 4: Remove AT&T micro-SIM and insert T-Mobile USA micro-SIM
Step 5: Ensure that WiFi is switched off. Tap on Forget this network to make sure that iPhone 4S doesn't automatically connect to WiFi
Step 6: Now toggle Airplane Mode OFF. iPhone 4S will start searching for carrier. Apple's splash screen will appear soon after that
The screen will now display an Activation Required message. Notice that Edge will automatically be activated. The letter E would be displayed in status bar. When that happens, wait for around 30 seconds.
Step 7: Turn off your iPhone 4S. Now turn it on again. Activation Required message will be displayed once more.
Step 8: One signal bar will appear. Tap on Use Cellular Connection.
Step 9: Take out micro-SIM card. Once again, Activation Required will be displayed again. Insert micro-SIM card.
Your GSM iPhone 4 running iOS 5 firmware is now unlocked on baseband 1.0.11 without needing a jailbreak. Be advised, you may need to repeat the procedure a number of times before you succeed.
If you face any problems, leave a comment down below and we will help you out.