[Liz]

If a scammer gets you on the phone, do this: Act very interested...
act friendly. Then when they are about to clinch the scam, say:

"Oops, forgive me, I have to hurry......my supervisor is calling me."

When they ask about your supervisor, say:

"I work for the FBI's telephone fraud unit."

[Buckeye McFrog]

I also got the “Microsoft Tech Support calling about a serious computer security problem” call.

I said “Oh, that’s good. My computer is a Mac. Can you help me with that too?”

-click-

I only pick up when I want to amuse myself by cranking someone.

[MHGinTN]

Another line that prompts their immediate disconnect is to let them speak their opening lie, then tell them “This is important. Don’t hang up. Our tracing software takes a minute or two to finish a thorough trace to your actual location. So don’t hang up!”

[sauropod]

You need lowbridge on the case!