Bank account debited wrongfully, now takes long to reverse

I rented a car on 27 Nov and paid the deposit of R1200. Yesterday out of the blue Avis debited my account with a further R 880. Apparently I phoned them to ask for extra insurance on tyres and windscreen. This did NOT happen. When I phoned them to query this they told me that it was an error on their side, they used the wrong contract number. I asked them to please reverse the debit on my account on THE SAME DAY, as it is unacceptable. On this morning 6 December the money still has not been recovered.

I am very unhappy about the service I receive, and I have to phone to follow up every time, nobody gives me any news on progress made.