If you mean that the FaceTime app is no longer on your phone, see the following from Remove built-in Apple apps from the Home screen on your iOS 10 device or Apple Watch - Apple Support
Restore a built-in app that you removed
If you mean that the FaceTime app is no longer on your phone, see the following from Remove built-in Apple apps from the Home screen on your iOS 10 device or Apple Watch - Apple Support
Restore a built-in app that you removed
Do you live in a country which does not permit FaceTime?
I want to get FaceTime on my phone but it says it’s not in your device what shall I do