These people are so rude and crooks. I paid off my...

These people are so rude and crooks. I paid off my auto loan and I get a letter in the mail saying I haven't paid and my account is delinquent. I call them to resolve the problem and they say you haven't paid. I said I have a confirmation number and that you need to look into this problem instead of just saying I didn't pay. So the rude man checked and found out that my load was paid off in full. I said exactly so why did I receive this letter and why you people are trying to defraud me. These people are terrible. I will never do business with them ever again.