This is my MO for unknown numbers these days (which I only answer when I have a reasonable expectation of getting a call from a new contact). Automated systems will just disconnect when they think they got a dead line. Humans will go, "uh, hello?"
I started doing this a few months ago, and the number of spam calls I've gotten from certain area codes that used to call me without fail at least three times a day has dropped considerably.
I've had good results from answering spam calls, following the prompt to get a human to "resolve this matter with the IRS" or talk to "Visa and Mastercard customer service" and just screaming into the phone when they come on the line.
Seems to get me on a "don't call this number" list after a few goes.