Richard, you've reminded me of a very similar incident.

I was getting collection calls for someone totally unknown to me. The caller gave a number to call "if this is not the correct number for xxx." Dumb me saw this as an opportunity to give the collectors a piece of my mind.

Well, although calls for that particular party stopped immediately, the floodgates opened and I was getting several unsolicited calls per day. Apparently they sold my number (I was smart enough to not give my name) as a "live prospect."