I ask them how poor they must be to become scammers and thieves. I say they must come from a dalit family. I say their mother's skin is the color of poop. I tell them their society is so gross that they shit in the street.
Whenever we're trading insults, I parrot whatever comes out of their mouths back to them really obnoxiously, because I already got my licks in, and they hate it when you mock their broken pahjeet Engrish. I also repeatedly ask them how poor they are, or how poor their parents are.
I ask them if they're from the stupid poor people who worship cows and elephants or the stupid poor people who worship muhammad.
Sometimes I pull up fake credit cards using an online generator and keep going on the call as long as possible. The cards don't work, so I play dumb and change a number in the middle and read the card number back to them, pretending it was a mistake. Then I tell them I was wasting their time on purpose because they're a scammer. They hate it and it gives me such glee.