Just after Apple released iPhone 4S from some time, users began asking about unlock for iPhone 4S, and since that users haven't got any word from the Dev Team blog about Ultrasn0w about if it is going to unlock iPhone 4S to work on any carrier or not, so that we have got some good news that all users want it just after the jump:
Thankfully some guys at MacRumors forum have got a way that will unlock your iPhone 4S without needing to use Gevey SIM or Ultrasn0w tool and also no jailbreak required, you can follow this steps and after it you will unlock your iPhone:
 

How to Unlock iPhone 4S, 4, 3GS without Jailbreak or Gevey SIM


Step 1: Insert original carrier AT&T SIM card
Step 2: Dial 611 for AT&T customer service hotline and drop the call
Step 3: Turn on Airplane Mode
Step 4: Take out AT&T SIM card
Step 5: Insert T-Mobile SIM card
Step 6: Make sure WiFi is off ( also tap on ‘Forget this Network” to make sure it doesn’t connect automatically later)
Step 7: Switch off Airplane Mode and iPhone will search for network. This is followed by the Apple splash screen appearing.
Step 8: Activation Required will be displayed on the screen
Step 9: EDGE network will activate automatically – notice the ‘E’ on the top left corner of the screen
Step 10: Wait for about 20-30 seconds and turn off the phone
Step 11: Turn on iPhone and the same Activation Required screen will be displayed
Step 12: When you see one signal bar, tap on Use Cellular Connection
Step 13: Eject SIM card
Step 14: Activation Required screen will be displayed the second time
Step 15: Insert SIM card - Unlocked!
You can watch this video guide that will help you to jailbreak iPhone 4S... We will keep you updated if there is something new update to these steps...