Unfairly debited by Dollar thrifty

I rented a car that was due for return on the 9th of April 2018, as per my agreement with them, I returned the car on that day and within the stipulated period, to my surprise on the 11th of April I saw a payment debited from account, when I inquired with the branch at OR Tambo, Shalen investigated the matter and confirmed that a refund was due to me because they mistakenly debited me, then after two day I phone the OR Tambo branch and spoke to Terry who said to me in a rude manner "according to their records they didn't debit me, therefore I will not receive the refund, I then said I will provide a bank statement as proof, I provided the bank statement to them were they asked me to give them up until Monday(23 April 2018) to get authorization from the manager at Hartfield. Today it's Wednesday I still have not received any feedback, I even sent an email to client services, OR Tambo branch and the manager at Hartfield, but no one has rep**** to me. Dollar thrifty treats their clients like garbage, I have never seen such POOR SERVICE!!!