Block unwanted callers in FaceTime on iPhone
In the FaceTime app , you can block voice calls, FaceTime calls, and text messages from unwanted callers.
Go to Settings > FaceTime > Blocked Contacts.
Scroll down, then tap Add New at the bottom of the list.
Select a contact you want to block.
To unblock a contact or phone number, swipe it to the left, then tap Unblock.
See the Apple Support article Block phone numbers and contacts on your iPhone, iPad, or iPod touch.