Extremely Poor Service and short change refund of my holding deposit

On 15 June 2017at about 17:02, I collected a vehicle from Dollar Thrifty at the Cape Town International Airport. Comments: A booking was made via Travel Jigsaw Limited. I was required to pay the following amount(s) prior to the release of the vehicle from my debit card as had no credit card in my possession:- (a) R6,000.00 as a holding deposit, (b) R2,500.00 for fuel. Total amount paid was R8,500.00. The return date was on a Sunday, 18 June 2017. However, due to unforeseen circumstances the vehicle was returned on the next day, 19 June 2017. Remarks: Email for extension was sent to Travel Jigsaw on 18 June 2017. The vehicle was returned on 19 June 2017 at the Cape International Airport. Remarks: It must be noted that the booking made with Travel Jigsaw Ltd was for unlimited kilometres. My refund effected was R4,949.37. Now the question arise - Does that mean that an additional day (one day) cost me R3,551.00? All my five emails sent to Dollar Thrifty seeking clarity have not been answered to date. They (emails) were sent on - 06 July 2017, 17 July 2017, 03 August 2017, 07 September 2017 and 06 December 2017.