This new feature allows you to manage unknown call settings by automatically screening numbers that match Google's spam database as well as callers that may be spammers using altered numbers.
In the resulting window (Figure A), tap Spam And Call Screen.
From the Call Screen settings window (Figure C), tap Spam.
How to use the Possibly Faked Numbers feature in Google Pixel 4 Back at the Call Screen settings window, tap Possibly Faked Numbers and, from the popup, select Automatically Screen.
Since enabling this feature on my Pixel 4, I haven't had to deal with a single spam call or spoofed phone number.