My favorite thing to say to a debtor who tries to get under my skin.

"AFTER SPEAKING WITH YOU BRIEFLY, I NOW UNDERSTAND HOW YOU ENDED UP IN THIS POSTION, HAVE A GREAT DAY"

That one line pissed off my debtor sooooo much, he called to complain to my manager, my manager like you don't like the calls then pay off your debt and guy ended up paying entire account in full.