If my caller display shows 'Unavailable' I either don't answer it or put it near the radio.... I reckon if they are unavailable to me, then I am to them.
If it shows 'Withheld',I usually answer as it can be a switchboard/doctors surgery/hospital etc, but I have the radio ready for any scammers to talk to.
I have no time for these people at all.
Many thanks Taz2 for posting the link to that video. It was amazing!!!