Dishonest conduct, incorrect billing, refusing to refund

I rented a car from King Shaka Airport. Collected it in the morning of the 18th of March. When I collected the car, the fuel indicator showed 686km worth of fuel in the car. When I returned the car on 21st March, I refueled, the fuel indicator showed 742km (Distance To Empty) worth of fuel when I returned the car. I took pics on collection and return. I was shocked when I got billed for refueling. I enquired about this and provided the pics I took with time stamps and locations and a Thabiso Hlabana responded saying a query had been loaded with the branch to credit me for the fuel they charged me.

To my shock, I got a response a Thuba Nkomo asking me for receipts of the refueling. I rep**** and indicated that between traveling from KZN to WC, I no longer had the receipts. He went o to tell me that I he cannot take my word for it. This is despite providing the photos I took at collection and drop of. I asked him to provide me with evidence the amount of fuel in the car at pick up and drop off, he just responded with the previous day's (17/03/2022) refueling note. Of course this does not show Distance To Empty or how much fuel was in the car. I find this to be dishonest business conduct.