AVIS - Appalling service, no communication

I am insured with Discovery. My car went in for repair and I was given an Avis rental car for use while the repair took place. The car wasn't great, but that's not the issue. Avis sent me an email telling me that a traffic fine had been issued, only the basic information. I have not been able to access that fine (R 750.00). They then debited my card with a further R 355.00 with no explanation. I filled up with petrol 500m from the return location so it can't be fuel. No explanation at all. And the refund of my (unreasonably diminished) deposit has not been made 2 months later. I have sent 5 emails and have not received a single response. This is appalling service. I shall be taking up the matter with Discovery and suggesting they change their rental arrangement!