When our son was younger (2 or 3) I'd hand the phone to him.
Once, in fit of boredom, I asked the caller in the area 30 or 40 of the stupidest questions I could think of. They were selling basement waterproofing and I asked things like what if we had a pipe burst, or the drain backed up, what if the window broke and water came in that way... he finally gave up after about 15 minutes.
Some of the best ones are from Tom Mabe
Tom Mabe Google search. I love the one where a carpet cleaning service calls him and he acts like he just killed someone...