New bug from Apple! Love my Apple devices but things get weird as soon as they mess up.
The latest, a bug within the new FaceTime update, specifically the group feature. To sum it up, even if you don't answer a FaceTime call that a friend initiates with you, they can still hear the audio coming from your phone. Even worse, if you ignore the call - they can see video captured from your phone! Crazy right!
Apple says this will be fixed by the end of the week, but in the meantime turn your FaceTime off to be safe.
Go to your settings > General > FaceTime > the toggle to OFF