Dishonoured booking

Hertz is the worst car rental company. I made online booking for unlimited mileage for a weeked and it was confirmed. I was supposed to collect the car at OR Tambo International airport at 22:30. One of the agents called to confirm the booking and arrange for me to collect the keys as I was arriving after their closing time. She took my credit card details to book the car and the depostit and said I had to pay R2000 fuel deposit which was not part of the quote. After everything was confirmed which wa 30 minutes before my flight, I received a call from the manager saying they can't give the car as my credit score was low. I would hav been left stranded at night without a car at OR Tambo had I not made other arrangements. This is unprofessional and nonsensical. I was not buying the car, merely renting for a weekend. I have been renting cars many times without any issues. What does my credit rating have to do with affordability?????????