We were getting a few a while back. These callers were the ones that would talk for 30 seconds before you could get a word in.
Decided to have some fun with the next one that called, so after they had finished their 30 second spiel, I politely asked them to hold the line, then switched on the stereo and put the phone down near the speaker. A couple of minutes later I came back, politely apologised for putting them on "hold", then asked them to repeat their 30 second spiel. At the end of that spiel, I said I was sorry but I would have to put them on hold again, and before they had time to respond the phone goes near the speaker again - this time for five minutes.
When I pick up the phone the second time, the caller is irrate and hangs up on me! I could have played this game all day and the wife was p*ssing her pants in the background! Whether coincidence or not, only had to play that game 1 or 2 more times before the annoying phone calls stopped.....