Hello bri800,
Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're trying to be removed from a Group FaceTime call and related messages. To be removed from the call, please follow this guidance:
Use Group FaceTime on your iPhone, iPad, and iPod touch
"When someone is added to a Group FaceTime call, they can't be removed from the call. The person who was added to the call needs to end the Group FaceTime call."
In that case, the one who starts the Group FaceTime would be able to remove members from the group. If you also need to be removed from the Group Chat, this article will also be helpful: Leave a group text on your iPhone, iPad, or iPod touch
We hope this helps.
Cheers!