why people do this?

My sister shifted from chennai to noida. She & my B.I.L. ( brother in law) hires a movers & packers company for their lugagges. But after 20 days they didn't receive their luggage. the owner of the company intially misguided them & now they came to know that their luggage is even today in Chennai. They already payed for the charges and now he is demanding more. I don't understand why people do this & cheats others.......I hate these type of people. These types of people are curse to our society. I hope GOD remove them soon from the world.