I used to not answer calls like this. Have had several calls to my cell in past days from all over the U.S. I can block a few numbers, but rarely see the same number twice. My voicemail sometimes catches the tail-end of a robo-call. I'm tired of clearing those messages. I now answer and immediately hang up. Don't know if that will invite more calls, but not answering wasn't slowing them down.
I get that scammers are scammers. I don't get how little seems to be done to crack down on them. Maybe too much profit in it for companies that enable it.