I went through a phase of stringing them along as long as I could. Last one I had phoned to say that there was a problem with windows on my laptop and he could sort it out if I was to give him remote access and some money. So I played along for a while assuming the role of a simple techophobe, happy to get all the help I could. When it got to the point of giving him anything useful I said:
"You'd think I'd know how to do this what with being Professor of Computing at Surrey University."
I don't even know if that role exists and even if it does I'm no professor. Needless to say it was him that slammed the phone down. Ahhh, what fun........