(Taken from my web)
You may need to disable cellular data network on your iPhone in some conditions, after tapping menus and wasting your time, you may find out it is impossible, or maybe you cannot find it!
Your first choice is right, it is simply impossible!
So, how you can prevent your iPhone from accessing cellular data network?
1) Tap Setting -> General -> Network -> Cellular Data Network
There, you will see some boxes to enter user name, password and etc. You need to enter some wrong data in user name and password boxes! Then turn your phone off and power it on again.
That's all!
And if you would like to use cellular data network again, you just need to roll back the settings you made earlier.
2) An alternative way is to simply ask your operator to disable cellular data network for your sim-card!
