Why can't I update my iPhone 4s to iOS 6?

When I go to the software update screen it says "ios 5.0.1 your software is up to date"
I even hooked it up to iTunes 10.7 (latest version) and it still says the same thing that iOS 5.0.1 is the latest version and my iPhone is up to date. I can't find anyone else with the same problem

Open your phone press settings, general, then press software update. You should be able to my dads phone is iPhone 4s is updated to ios6. If that doesn't work then go to iTunes on your pc and press the update phone option if that doesn't wok too, then back up your phone on iTunes. Take your phone and go to settings, reset, then press erase all content and settings so your phone can go back to factory settings so it'll be like a new phone but remember to take out sim card before you do the erase part. If all this doesn't work contact apple customer service.