Product: Credit card or prepaid card

I rented a car with XXXX / XXXX and my reservation was for a total of {$300.00}. The rental agreement confirms that amount in Euros ( XXXX ) and also states that a XXXX deposit will initially be charged to my card along with the rental price. Based on that, I should have been initially charged XXXX Euros ( XXXX + XXXX = XXXX ). 
Instead, the merchant charged me {$660.00}, and upon return of the car refunded the security deposit of {$260.00}. Upon subtracting the security deposit from the initial charge, I realized that I was overcharged by approximately {$100.00} ( {$660.00} - {$260.00} = {$100.00} ). 
When my attempts to contact the merchant in XXXX, XXXX, failed, I decided to file a dispute with the credit company that issued the card that I used to pay for the rental. 
XXXX XXXX XXXXs dispute resolution is completely dysfunctional and I suspect that it is designed to be so. Following an initial credit for the disputed amount, XXXX XXXX quickly informed me that upon review they noticed a refund from the rental company that exceeded the amount of the dispute. They quickly and erroneously concluded that the dispute was resolved and charged back to my account the disputed amount. I explained over the phone that the refund that XXXX XXXX was showing was for the security deposit rather than a result of the dispute. To continue with the dispute, XXXX XXXX requested that I deliver evidence supporting my position, and they provided a secure link through which to upload the evidence. When I uploaded a copy of the rental agreement, XXXX XXXX claimed that it was not legible. Needless to say, the copy was perfectly legible when it was leaving my computer. XXXX XXXX then provided another secure link and requested that I send the agreement one more time. I complied with that request only to learn by phone that my documents were never received. At that point, I asked for an alternative mode of delivery. XXXX XXXX provided two fax numbers, and I faxed a copy of my documents to each one. No action was taken by XXXX XXXX, and I followed up by phone. When talking to an agent who identified herself only by the first name of XXXX and employee number of either XXXX XXXX or XXXX  XXXX, I heard a long list of explanation why XXXX XXXX would not be able to assist me. First, XXXX offered to be " honest with me '' and informed me that my documents were delivered past a deadline of XX/XX/XXXX. She was not receptive of my explanation of why the first two attempts to deliver my documents on time did not work. Next, she attempted to argue that the rental agreement that I provided was not really an agreement. Instead, it was just an estimate of prices. I pointed her to the section of the agreement that clearly stated that we were looking at the Rental Agreement Summary. I also explained that the pricing reflected in it may have had some contingency built into it to cover instances such as late return, failure to fill up the tank etc. And that only to that extent, the prices were estimated. But since I returned the car on time, full of gas, and with no damages, the pricing was final. As a last resort, XXXX insinuated that I had " doctored '' the rental agreement in two ways ; a ) things were " handwritten '' into the contract, and b ) half of the agreement was cut out by the way I zoomed in on it to take a picture. I explained that the rental agent wrote by hand the relevant portions of the contract into their template, and had me sign it also by hand. Upon return, another agent handwrote additional input such as mileage, date and time of return, as well as that the tank was full, and the car showed no damages. She refused to accept that there was only a small margin on the left that did not fit into the picture. She also refused to receive a better copy which I offered to deliver. Throughout this combative discussion with XXXX, I requested repeatedly to speak to a supervisor, but each time she claimed that she was the supervisor. She finally gave in to my request and handed the call to another supervisor still arguing that there was nothing else that XXXX XXXX could do to assist me. The new supervisor went over my documents, confirmed that they were received on time, and did calculations. She also reached out to the rental company whose representative in the US promised to obtain more information from their international reservations. As of today, more than two months after I returned the rental car, I am still being overcharged by {$100.00} and XXXX XXXX has done absolutely nothing to bring a resolution.