I loved the one I got that purported to be from 'Microsoft support' about a 'serious condition' on my Windows computer. I let them jabber for a while, and then tried to play dumb as they tried to talk me through 'fixing the problem' by logging into a website and giving them control of my computer so 'I can further repair this enormous issue'.
I wasted probably 10 to 12 minutes of their time. The guy said 'click on the start menu', so I said 'Okay. Where is that menu?' At the bottom of the screen. 'Okay, where at the bottom of the screen?' -- and on and on --
The guy started to get frustrated, probably because I was wasting his call time, and got testy. I finally said 'Oh, I'm using a Mac. Why would Microsoft be interested in a problem with my Mac when I'm not running any Microsoft software on it?' He stuttered for a minute, and said they at 'Microsoft' knew it was a Mac, and they are still concerned about a serious error on my computer. Then I told him 'Yeah, nice try ******. Your poop might work on unsuspecting rubes, but I'm in the IT business and I KNOW you are a scammer! Eff off, and have a nice day!' I think he actually beat me to hanging up. I have never received another call like that again. My poor mother-in-law wasn't so lucky. She got at least 2 or three a month, but she seemed an easy mark for them I suppose. When she moved in with us, I finally got to the phone when they would call, and they stopped called her too, eventually.
The reason these, and phishing emails are out there is because they work! If they didn't find stupid gullible people, they wouldn't be doing them. Sad to say, but yeah...
But keep them on the line as long as you can. Play stupid. Start tangents at times to blow their time. They are monitored, in their sweat shops, for how many people they call, and how many of those people they can con. The longer they stay on the phone, the worse their numbers are. Or start asking them outlandish questions. Like 'what color is your underwear', or 'what's your favorite sexual position'. Your number will get a mark in their database, and they won't call you, and those scammers trade lists, because they always share the good marks. Make yourself a problem, and they will not wast time on you. Like Jehovah's Witnesses. They stopped coming to my house. The last 4(!) (I swear they were using me to train their door knockers at one point) stood for over an hour as I blew everything they said out of the park. They know enough not to stop here...
Good luck... I HATE scammers...