One of my favorite things to do is multi-line what I like to call fly-by-night scam centers, which means that the phone number will probably cease to exist in a matter of hours. I start to call them one line at a time, insulting them, mocking them, laughing maniacally or pulling some other shenanigans before creeping in other lines one by one, eventually taunting them that every time they pick up the phone, it’s going to be me. I’ll even change my voice in an obvious way and say something to the effect of “this is totally someone else and not the same guy”.
Then, and here's where the real fun part comes in, after so much time passes, I will wait 5-10 minutes and have my girlfriend call and actually pretend to fall for the scam and right when they're about to get her personal information, I get on the mic and say "just kidding, dipshit. Still me. Did I not explain how this works? You pick up the phone -- it's me." or something like that.
This has almost always made that call center shut down immediately afterwards. I presented false hope just to crush it. So now I just need to come up with a name for the games and fun highlighted above.