I kind of enjoy some messing with the spam calls. When I'm in the mood it's a source of entertainment. The goal is to confuse them. Whatever pops into my head at the moment. Often times I pick up the phone and don't say anything. If the line gets disconnected, I guess it's a computer and took a call before me.
Sometimes I just start off with, "What ever you're selling I'll take a dozen. When can you get them here? What color will they be? Can you overnight them? The last shipment was busted when I open the box. They quickly hang up.
One of my favorites is to say. "Hello ....(city of choice) police dept. Homicide--sergeant Hall speaking. You have a homicide to report? Is this an emergency? Do I need to call 911 for you? Is someone bleeding? Did you shoot them? I just keep asking questions, speaking in a firm, fast tone. They just hang up.
I've messed with the folks going to fix my student loan so bad one guy called me a M-Fer and hung up!