Q: How do I turn off 3G on the iPhone 4S?

Depends on which radio chipset Apple chooses to use and whether they include that capability. On some of the current LTE phones the reason you can do that is they have separate radio chips, not one hybrid chip.

When I was using iPhone 4, I always turned off 3G and only let the phone running on EDGE, which is enough for me to receive push notification and checking tweets, and the battery can last for ~1.5 days with everything on. But with 4S, due to there is no option to toggle off 3G, the phone can barely last for half a day, and I have to charge it twice a day.

Apple said they are working on the remaining battery draining issue which couldn't be fix on iOS 5.0.1 and it's been 3 weeks since the release of iOS 5.1 beta 2. Hopefully Apple is working with Qualcomm to release the firmware update to restore the 3G on/off switch.

We can now turn off 3G on iOS 5.1 beta 3, yay.

Yes, the ENABLE 3G button is available on 5.1 beta 3. It should be there in the final 5.1.

When will released the 5.1 with switch 3g/2g?? We need it

AGREE!!! But even more I need the iPhone 5 ... still waiting!

I just did the update and I don't have the enable 3G button back. My phone will still be a paperweight for 8-10 hours a day.

What carrier are you on and where are you located?

Tucson, Arizona and I'm on AT&T.

Unless it will require a carrier update, which is possible but not likely, it may be as others have said, that AT&T is turning off the EDGE frequencies so they asked that it not be included for their phones.

We all know by now that the ENABLE 3G button is intentionally removed by Apple, it's not due to hardware constraint and poeple who need the ability to turn 3G off should avoid the 5.1 until tool that can not be named becomes available.

Hey guys! I have the enable 3G button back!! I live in Lima, Peru; my carrier is Movistar (Telefónica)!

It's safe to update to 5.1, ENABLE 3G is back.

What carrier do you have? I updated and I don't have the button. 

I am on Mobifone in VN, a GSM operator having 3G and 2G.