FaceTime Spoof calls?

I have been receiving FT spoof calls from my girlfriend's phone. Here's the catch: the calls were coming to a new second iPhone and I have where I hadn't given anyone my new number. So I was not showing FT calls to my existing and old phone but my new iPhone. So we decided to turn off her iPhone. When her phone completely powered off I got a Spoof FT call from her number. I decided to answer with my camera off and finger over the camera. Nothing came from the other end, only a black screen and silence.

I called apple support, who hung up on me. So I was on my own to try to figure out what had happened. I have received spoof mobile calls in the past. This is the first time ever that I have received spoof FT calls. I was able to find; according to an online source that contacts can be taken from any app that has been hacked if you have shared your contacts with that app. Eg. Social Media apps, Banking Apps, Video communication apps, gaming thread apps and the list goes on.

I have gone in and removed contact sharing on every single app I have. I cannot say that the damage hasn't already been done.

Has anyone else out there had FT spoof calls? How are spoofers accomplishing this? Short of geting new phone numbers how do I stop the spoof FT calls from coming through?

I'd call apple support but they'll just tell me that what I am explaining to them is impossible and hang up on me.

Thanks all,