I have an iPhone 4 (not s) and I use straight talk. I tried to FaceTime my friend and noticed you have to use wifi… Well I don't have wifi! I read you can go to settings, FaceTime, turn use cellular data on. But my phone doesn't say that! Idk why so yeah how do I get FaceTime to work?
How to use FaceTime over cellular data with straight talk?
Unfortunately FaceTime is not designed to be use over mobile data. However you can make it work on mobile data when you have jailbroken iphone.