SHOCKING SERVICE

I made use of Bidvest Car Rental in April 2019, and after using the service noticed a deduction from my credit card which was considerably more than the contracted amount. No invoice was sent to me. I wrote to the agent, Ricardo, in Herm****, but received no reply. As I could not call him (I was overseas), I wrote another mail to him, but once again received no reply. I then wrote to the Head Office, but did not receive a reply either. I followed that up with three more letters, but to date I have received not a single reply other than a computer generated acknowledgement that they received my letter. IS THIS COMPANY STILL OPERATIONAL?