How to downgrade carrier settings from 4G to 3G?

Hi

Two days ago my iPhone 5s prompted me there was an update for my carrier settings, so I did without knowing what that update was.
The update included a toggle that allowed me to enable 4G, previously this was the toggle to enable 3G.
Since I always use EDGE because 3G drains my battery too much, I never enable it. After the update, when I disable 4G, it automatically switches to 3G, which is equally battery absorbing.
So I restored my iPhone to a backup before the update but the settings are still there.
I hope one of you guys have more knowledge about this topic...

Thanks!

Lorenz