Airportrental.com. Stay away

We rented a minibus on 18/09/2019 at Cape Town Airport. On return I found that the quoted tariff was much lower than they deducted from my credit card. I have been sending countless e-mails over the past few months, and although they agree that there is a problem, never solved it or refunded me. This is now 10 months later and still no result, either from them or Thrifty where I got my rental from