So it seems to be mainly a U.S. issue, I'm guessing (though @mathrania is in India and has the same issue). @sindre2104 showed that he can use the toggle right out of the box, but his carrier is Telenor from Norway.
I'm also noticing a lot of subtle but noticeable differences in each device screenshot presented, for instance my device says "flashlight" rather than "torch" in the toggle window, among other things.
I simply can't figure out why they would remove the feature in certain countries while leaving it there in others. There's no viable explanation for it
How do you know?
@tool2269 do you have an app similar to AT&T's "Usage Manager" app installed to toggle your data as well?
You need to edit the others.xml file in System/CSC on your device. When you open the others.xml you will see the csc code. Edit the line that says ConfigDefQuickSettingItem and add MobileData on the end. After editing make sure to set permissions if they changed to 644. I used root explorer to do all this. After editing the CSC go into settings, general then reset settings on your device. When it reboots go to edit the quick setting icons and the Mobile Data Icon will be there.