Product: Vehicle loan or lease

I had an accident that totaled my car. My insurance paid on the claim. I had gap insurance that I purchased at the time of the sale. Nissan mailed a package to the insurance the gap insurance company and myself. I assumed all was well as I did not hear anything. I assumed the claim was fully paid. It wasnt until months later that I found out through a phone call from Nissan that I was in collections. I explained to the lady on the phone this cant possibly be. She told me I did not make payments. I told her that simply was not true. She explained I owed {$1900.00} and that it was for missed car payments. She really wasnt receptive about hearing me so I called XXXX the gap insurance company. They explained to me that three letters were mailed out asking for a Bill of sale. I explained that I never got them. I told her I would work on getting the bill of sale to her immediately. I was so infuriated by the representative from Nissan who told me emphatically, that I was in collections due to nonpayment, that I just had to call back. I explained to XXXX I was not delinquent in my payments. That it was in fact because The gap insurance company needed a bill of sale. She continued her delightfulness with me and told me I was a liar because it was mailed with my packet of information sent to me and to the gap insurance company. I looked in my packet and my bill of sale was not in there either. It was not included in the packet of information that was sent to me nor the gap insurance company. ( First error ). I called the gap insurance company back and through conversation I learned why I didnt get those three letters they had mailed me requesting the bill of sale. On the day of purchasing my car at XXXX Nissan, the gentleman entering the information failed to put my apartment number on the gap insurance addendum. ( Error two ). I live in a huge complex in the city of XXXX. Without an apartment number there is no way I would receive these letters. I was at work at the time and I called XXXX Nissan. I explained the situation to the gentleman that answered the phone. He was very helpful. He was able to get me a bill of sale within a couple of hours from Ohio and faxed it to me and to XXXX insurance company. The reason why he was so helpful and really went above and beyond was because he felt badly about the critical error they made at his dealership. XXXX received the bill of sale. They released the money to Nissan about {$1900.00}. My final balance was {$21.00}. Which I paid immediately upon learning this. My credit took a major dive. My credit report states that I was in collections with Nissan and it was a charge off. I would have never been in collections with Nissan if they had the right address put on the Gap insurance Addendum. They failed. And the amount was certainly not not not a charge off. My gap insurance company and I paid the balance in full. When I saw my credit take a major blow, I called Nissan and asked what they were going to do about this. They said, dont worry it will go back up. Well, it hasnt. If it wasnt for XXXX Nissans error at the time of sale, I would not find myself in the situation that Nissan caused me. 
I was assured by XXXX, the gap insurer, they were taking good notes. They were kind enough to fax me a copy of the final notice I never received. You can see my incomplete address there and in the original addendum from Nissan. I also included the portion of the bill of sale from Nissan with my complete address. Clearly an error by the man at XXXX Nissan. 
Please help! Nissan will not address this even though it was their error. And they were paid in full in the end. What charge off Nissan? Btw, Ive had two Nissans since 2014 and never missed a payment. Thanks Nissan!!! 
Oh, I replaced my car with a lovely XXXX!