My iPhone 4s work on 3G only with iOS6

IOS6 cannot add to the hardware ability of your phone, but all of the old abilities should still be there.

are you referring to wanting to use 4g or wifi?

What Service Provider do you have? Because some carriers don't support 4G.

It is a 3G phone. If on Apple or t-mobile you can get the psuedo 4G speed but the LTE only just came out for the iPhone 5