Open the Settings app
Tap FaceTime
Turn off the FaceTime switch
On Mac, open FaceTime
Click FaceTime in the menu bar
Select Settings or Preferences
Uncheck Enable this account or sign out of FaceTime
On Apple Watch, FaceTime cannot be turned off separately
On iPhone or iPad, you can also disable FaceTime in Screen Time restrictions
Go to Settings
Tap Screen Time
Tap Content & Privacy Restrictions
Tap Allowed Apps
Turn off FaceTime