What should I ask people who maliciously don't pay the bill?

Use the little magic of tinfoil to help you get rid of the guy who borrows money and doesn't pay it back. Tin foil paper is a silvery white layer inside a cigarette case. First, please make a boat out of tin foil, make a small flag, write the name of the person on the flag, and then put the boat into the river or pond. Soon, the money will be returned to you. (for entertainment only)

Seriously, you can stick the IOUs in a conspicuous place in the classroom or the company. As long as he feels a little ashamed, you can get the money back (you have to open another piece of paper to explain that he is paying back the money, otherwise people will think you are crazy). If he is really thick-skinned, you have to take extreme measures, such as knocking on his door every day and calling him in the middle of the night ... Besides, I don't think you can go to a debt collection company no matter how much money you owe. I think that's too dangerous. As long as violence is not used, the method quota should be completely fine. You are evil, I am more evil!