If you have Stolen Device Protection set to Away From Familiar Locations:
When you are prompted with Face ID, keep tapping Try Again, after a few tries you will be prompted with entering your passcode. Thus starting the 1 hour security delay for turning it off.
If you have Stolen Device Protection set to Always:
Sign onto iCloud.com/find with your Apple Account credentials, find your iPhone in your List of Devices, select Remove from Account. This will remove Find My and also Stolen Device Protection. Then turn Find My back on and leave Stolen Device Protection off. If this doesn't work you'll have to erase your iPhone from there.
Then get your iPhone’s Face ID serviced at your nearest Apple Store Genius Bar or Apple Authorized Service Provider. Genius Bar Reservation and Apple Support Options - Apple