Change FaceTime audio and video settings on iPhone
You can change the audio and video settings in the FaceTime app at any time during a call.
Change the settings
Tap the screen to open the controls, then do any of the following:
Switch to the rear camera: Tap (tap it again to switch back to the front-facing camera).
Turn the sound off: Tap (tap it again to turn the sound back on).
Turn your camera off: Swipe up from the top of the controls, then tap Camera Off (tap again to turn it back on).