How can you disallow people from joining an existing facetime call? My son was on a facetime call with a friend an they both did not answer but the friend was able to join their call with out their permission. Is there a hack?

Hello yianni420,

Thanks for posting in the Apple Support Communities. We're happy to look into this with you.

We want to clarify; do you mean a 3rd person was able to join the FaceTime call? If so, is it possible that the actions from the page visited before posting, Use Group FaceTime on your iPhone or iPad - Apple Support under section: Join a Group FaceTime call could be what has occurred?

Join a Group FaceTime call 

There are a few ways to join a Group FaceTime call that someone else started:

* Tap the notification from the Notification Center or the Lock screen, then tap the FaceTime button . 

* To join a Group FaceTime call from Messages, tap the notification at the top of your screen or tap Join from the group conversation in Messages. After you tap Join, you're automatically connected.

* To join a call from the FaceTime app, just go to the active call in FaceTime, then tap the FaceTime button .

If you have concerns about what has occurred, it would be best to report this to Apple so they can investigate. You can reach out to them directly at Get Support.

Best regards.