Q: iPhone 4S unable to turn off 3G?!

Hi, i don't have the option to disable 3G, why is that ?

If you telecom service provider doesn't support anything less than 3G you cannot turn it off.

Did you READ this thread at all before you posted this question?

Settings -> Cellular -> Cellular Data

This will turn off your 3g, wifi, 2g all but amazingly i can turn on wifi alone and accessed internet. It worked for me...

Description for disabling Cellular Data

Turn off cellular data to restric all data to Wi-Fi, including bla bla bla... this means you can only access Wi-Fi no 2G or 3G... hope this helps

I don't know if it's a UK thing, but I couldn't find "Network" or "Cellular Data" in my "Settings > General".
Though I did find "Settings > Mobile Data" which I could turn OFF.

Source:

http://www.pcadvisor.co.uk/how-to/mobile-phone/how-turn-off-3g-data-on-iphone-32 76632/