Disappointed service from Avis

I rented a car from Avis in Cape Town airport and 2 days before it was due, the guys from their tracking department came to fetch it because my brother was washing it and just because I was not there with him at the time, he asked to call but they refused, I then went to avis offices the next day and spoke with Rafique who promised to make a follow up and come back to me but I'm still waiting, and while waiting i got an invoice of R12862,from them I don't know what is it for.