Getting a late fee for paying too early

I will not mention the company here but we have a car loan on our most recently purchased car. I should also mention that we have been paying regularly on this car and not only regularly but early based on when the money comes in and not based on the due date except for the fact that it is not late. I got a letter in the mail today saying our loan on the car was delinquent. Some genius at the bank labeled one payment not as one of our regular payments but as pure principal payment and thereby we were late. To make it worse, it had become not late not because they caught the error but because the next month's check went in. Not surprisingly, I got an apology for the mislabeling of a payment and it was corrected. With service like this, no wonder there is a credit crunch in this country.