PNC Bank Auto Loans , Almost Repo After Their Error & Gave Bad Credit Report! Pekin Nationwide

Back in 2011 I made the mistake of getting a loan from PNC bank when I purchased a car.
I could not imagined the nightmare it would be.
I always made my payments on time. Never missed one. When suddenly about 6 months into the loan I start getting multiple phone calls from them saying I missed a payment. Which I hadn't . I go into the branch into morton and was told that since my co-signer was first on the loan they couldn't discuss it with me.
Well when they called me again about them I explained this and was told that was not correct and to go back in again. Which I did and was told the very same thing.    Well they started calling me all hours of the night. Even 1 am. Then began calling my co-signer. I kept telling them I didn't miss a payment and had all the recepts . They wouldnt listen or let me show proof. They kept saying they needed a full payment right away or they would take my car. 
Well not time they called I informed them that I contacted a lawyer to file a law suit against them. Suddenly they decided they should look into the issue. Well they found that since I paid my payment on the 30th of the month prior to the payment they claimed I missed it was applied as a extra payment for that month instead. I was then told normally if its with in two weeks of the due date they don't do that. But there must have been a error. 
However was assured this was corrected. 
Calls suddenly stopped. I thought all was well. I  was wrong.

Move forward about another year. I paid a payment on the due date at the branch in morton Illinois. Next day they began calling me yet again saying payment was late. They did this for two days. 
Next month I paid at the Pekin Illinois location on the due date and no issue. After that I paid at Morton again this time day before my due date. Suddenly calls began again. Apparently if I pay at the morton location it takes two or three days for payments to post to the account. 
But I was told that it wasn't a issue since it was before the 15th which was the date they considered it late.
Well recently I decided to check my credit report as I'm thinking of getting a new car. Well my report shows I missed a payment. So I filed a dispute. Because it was the exact dates they had the mistake on in the first place. Well they then just updated it to say I was over 30 days late. Which I never once was.
So my credit has taken a hit due to their error . No one seems willing to correct it ether.