Billing Errors

I rented a car from Avis on the 15th of November 2017 at Cape Town airport. To my surprise I received an invoice for 3 days rental on 8-10 November when I was not even in Cape Town. I sent a complaint to Avis but now 2 weeks later this has not been corrected yet. I received no credit note for the incorrectly billed rentals and off course my credit card was charged for these. No refunds received either and no feedback about when this will be corrected is forthcoming.. This international Company is acting like a corner cafe.