I am having the same problem with iMessage and FaceTime. I have an iPhone 4S that had iMessage and Facetime stop functioning. In settings I keep receiving the "waiting for activation" message. I have cycled the device on and off several times and have reset the network settings. No luck in reviving the applications. My iPad is functioning fine however.
Just did what you suggested on my wifes phone and can't locate the way to turn Data on in Settings. Where is it?
Nothing that says Data anywhere, not in Settings or in General/
I signed into Wi-Fi and am connected. I then turned on iMessage and facetime, both are waiting for activation 5 minutes later.
Great, did I now screw up her messaging too by trying to fix Facetime?
None of these things worked for us.
We went to the Apple Store and what I suspected needed to be done was correct.
Backup to iCloud.
Restore to factory settings
Download and install all of your content from iCloud.
Facetime immediately worked.
The Apple Store employee said he had seen several people with the same problem and this worked for them. You might backup as much as you can to your computer first, then to iCloud. I mean manually sending things to your computer first, like photos that you've taken with your camera you don't want to lose. Probably unneccessary but we did this first and I felt more comfortable.
iCloud backup and download worked fine but I hadn't done it before so I was a little leary of it.