I have gotten fewer spam messages when I respond with other spam messages I have received. They think they got another spam number and remove it. If its a call, sometimes Ill answer, and mute the line so they cannot hear anything. I just wait it out, I don't get repeat calls after a few of those. if the person setting up the call system is caused any form of financial damage or risk for me tying up their lines, and costing them both literal money per minute as well as missed opportunity to scam some old person, I don't mind doing a little here and there. As a treat.

Good for them, they've yet to get anything else out of me but my contempt but they're welcome to keep trying; my spam filter usually works anyways so the only time I even get to see these messages is when I have to check my spam folder for something.