AVIS 450km per hr car rentals from Durban airport.

Got an AVIS rental (VW Polo) to get from King Shaka airport to my home in the KZN midlands. And did a drop-off the next day at Oribi airport (AVIS) in PMB. Everything went to plan except after the drop-off, they then deducted almost R30K from my bank account (They invoiced me for over 10,000km). I've sent messages to them with phone pics I had of the speedo before and after (proving I did less than 200km). But no response at all so far (don't care if they don't want to answer - but give the money back!) Can't understand how the invoice even got produced - The rental period was 22hrs so the car would need to fly at over 450km/hr for the entire period to make up 10,000km.