Thrifty and the double debit

I rented from Thrifty all went well until one day as with a lot of car rental companies in SA it all went wrong - I handed back the car with a tank filled and gave the petrol slip to the attendant to show I filled up - they proceeded to charge me R648 for fuel (I drove 204 kms) and then double billed my credit card for 2 amounts of R648 = total R1296 - to cut a long story short - it took me 2 months of emails and phone calls to FINALLY get refunded - there is obviously something dishonest about Thrifty - they double debit your account and charge you for fuel hoping you do not notice and if you do they make it as difficult possible to get a refund