My old man used to get really surly and say "You're not fooling me buddy, I know who your are. Your that guy seeing my wife behind my back. Yeah, didn't think I knew about that, did ya? Well I got news for you. I just about got who you are figured out." No matter how much they insisted they did not know what he was talking about, he would just come back with something like, "Hey buddy, you're not fooling anybody, I know what's going on. How stupid do you think I am?" They always gave up after a few minutes and rarely called back.
My favorite was from my brother who recieved a call about insurance on his credit card account. He asked, "Is this so, if I die, my credit card is paid off?" "Exactly"' the guy responded, sure he just made the sale. My brother responded, "If I'm dead, I really don't care if my credit card is paid off or not." The guy gave up and never called back.