Complaint sub-issue: Credit card company isn't resolving a dispute about a purchase on your statement

My wife and I rented a car from XXXX XXXX located in XXXX, XXXX, CA on XXXX XXXX 2020 for 1 day. The representative at the counter told us we should take pictures of the car before renting because there were several customers disputing extra charges that the owner claimed were for damage to his cars. Our car was probably 10+ years old, with a lot of dents and scratches all over the car, as can be seen in the photos. When we returned the car, no one was at the office so we called and the owner said take the car back to our hotel and the rep would come pick the car up. 3 hours later she came and got the car. An hour after that she called and said the owner ( who was out of town ) said the car had a scratch on it ( how did he know this? ). She drove the car back to our hotel and showed us a white mark on a place on the car that somehow neither she nor we had captured in our photos. We took a photo of the white mark ( image # XXXX ). 
He never contacted us again regarding this issue. A month later I contacted Citi because the {$500.00} deposit had not been refunded, and called XXXX, the owner of XXXX XXXX XXXX XXXX. He said " You scratched my car! '' I asked whether he had any intention of contacting us or was he just thinking he'd keep the deposit with no communication to us, and that we did not scratch his car. He ended up screaming at me and hanging up on me ; at which point I wrote an email to him, and contacted Citi. Citi told me to cancel the card and start the dispute process, and gave me the direct phone number to the Dispute department ( XXXX ) and the disput ID # XXXX XXXX. Please see the attached email chain between XXXX and myself - there is more information on our experience with his rep and himself. Basically I wrote that a ) we did n't drive near anything that would have made at " scratch '' in that area of the car, b ) the car had scratches and dents all over car, none of which had been repaired, c ) the representative picked up the car from us and drove the 3 miles back to the rental office, the 3 miles back to our hotel, and d ) the contract declared normal wear and tear being included in the rental price and that the scratch was barely visible compared to all of the other damage to the car. He replied by asking for my credit card information! 
To my mind this is ridiculous that he even tried to charge us - the " damage '' was probably there when we rented the car, or the rep might have done it on the way back when she had possession of the car ; there is absolutely no way that we could be deemed responsible and charged for this. 

There are 20 photos in all, with # XXXX being the one my partner took when the rep drove the car the 3 miles back to our hotel to show us the " damage '' he was claiming we did. Again, he wasn't even in the locality, and we never spoke to him, only through the rep. He never supplied an invoice or bill for the extra charges. 

I contacted CitiI contacted Citi a month after submitting the dispute. I spoke to " XXXX XX/XX/XXXX at XXXX pm, who told me there was " no direct phone number for billing disputes, but she could connect me '' ; I was hold for 25 minutes then was disconnected. I called the Dispute line again and spoke to " XXXX '' who had no idea what XXXX had been talking about re the Dispute phone number. She told me the dispute had been filed in the wrong department and would be re-filed. I then sent the ( attached below ) files, emails, photos, and statements clearly outlining the events on XX/XX/XXXX2020. I received an email form Citi on XX/XX/XXXX thanking me for sending the dispute details, and that they would be in touch if any other information was needed for their investigation. 
I received a letter for Citi on XX/XX/XXXX stating " the case had been decided and the payment was being awarded back to XXXX XXXX XXXX Rentals, with no further explanation. I called Citi on XX/XX/XXXX and spoke to " XXXX '' at XXXX XXXX. She told me Citi hadn't looked at any of the evidence, that if a merchant " disputes the dispute then it is automatically reversed back to them, and I could appeal the decision by sending in the supplied letter signed and dated ''. EXPRESSLY stated in that letter was to NOT send any documents with the letter, but to send all my documents separately. I asked XXXX why they didn't even look at what I'd sent before making a decision, and why I'd need to re-send documents to the same address I had already sent them to. She put me on hold to speak to a supervisor and came back saying she could " open the documents and see everything, and I did NOT need to re-send anything ''. She told me Citi would be in touch with me if they needed any more information for their investigation. I received an email form Citi on XX/XX/XXXX thanking me again for my submission of the dispute details. 
On XX/XX/XXXX I received a letter form Citi stating " We received your response ; however, the letter is only signed and dated. Since the letter you returned is incomplete as a result, we have no further means to assist you in this dispute ... we now consider this investigation complete '', and I owe the amount fraudulently charged by XXXX XXXX XXXX to Citi. 
The word " incompetent '' describes for me the entire response of several departments and representatives of Citi. The obvious facts and evidence regarding this fraud that I sent to Citi was never even looked at. XXXX XXXX Rentals never supplied an invoice or receipt or any other communications defending their keeping of my deposit. The pictures of the car show multiple scratches and dents all over the car that had never been repaired. The employee working there told us to take pictures of the entire car because several other renters were disputing what they said were false charges the owner was attempting to charge for damages! His own employee told us this. 
I would like Citi to credit my account for the fraudulent charges, as they should have done months ago - there motto is " Citi is at your side before, during and after every purchase ''. I disagree, and just want them to credit my account for the fraudulent charges they are refusing to investigate competently.