Hacker Loktar_Sun has discovered how to easily unlock your iPhone 4S—and any other iPhone. The unlock will free you from your carrier's tyranny, which is great news, especially while traveling or switching companies.
You will only need a jailbroken iPhone, see here how to. The rest is painless:
Step 1Go to Cydia and add repo.bingner.com as one of your app repositories. Search for Sam Bingner's SAM package and install it.
Step 2Click on SAMPrefs icon.
Step 3Go to utilities. Select De-Activate iPhone. Make sure your iPhone is deactivated under More Information.
Step 4Click on By Country and Carrier in Method. Then select your carrier.
Step 5Click on More Information again. Copy your IMSI (International Mobile Subscriber Identity) in SAM Details.
Step 6Click on Spoof Real SIM to SAM.
Step 7Go to the main SAM menu and change the Method to manual. Paste the IMSI in the field.
Step 8Connect the iPhone to iTunes. It will reactivate your iPhone.
Step 10Disable SAM in the SAMPrefs app.
Step 11Connect your iPhone to the computer. iTunes will start up and tell you it can't activate the iPhone.
Step 12Close iTunes and open it again.
Step 13This time, iTunes will activate your iPhone and it will be unlocked! You will be able to turn off your phone and do whatever you want. The unlock will keep working, at least until Apple releases its usual countermeasures in a firmware update.
If your push notifications stop working, go to SAM again and click on Clear Push then connect to iTunes again. More here.