We have call screening on the landline so they never get through. If I have time & get a call on my mobile my alternative persona Mr R Soul who has an email account at mickeymouse.com leaps right in.
The best is to cut the call just before they try to close the scam or if they ask for a card say yes I have the ace of spades.

I feel wasting their time is a publicservice as they aren't scamming others.