Hertz Car Rental SA are *****s

I rented a Renault Clio in the evening of the 13th of September 2019 at O.R Tambo, for a period of 10 days, with the original return date of 23 September 2019. On 23 September 2019 I realised that there still a couple of errands I needed to attend to and decided to request to be granted an extension. I ended up extending till 28 October 2019, which is the day I dropped off the car at O.R Tambo. On the 21st of October 2019 an amount of R5150 was deducted from my account, and when I called the contact centre to query this, as the deposit had already been taken on the 13th of September 2019 when I collected the car, only then was I told that if you keep the car for more than 30 days they are obliged to deduct the deposit from your account. I didn't really have a problem with that 'coz I knew that the deposit is refundable, less the gas fee, provided the car is returned in the condition that one found it in, as the extension that I kept requesting timeously was taken off my account as and when I called in requesting to be granted an extension. When I returned the car on the 28th of October 2019, the gentleman who attended to the car assured me that all was in order, before I could leave the airport. So now this morning I receive an amount of R2608,14 from Hertz and when I call to query this I get told that this is what's due to me 'coz I kept the car for longer than 30 days, not forgetting that this was only communicated after I had queried it with them, and some additional charges, which I know nothing about, kicked in. According to my knowledge the deposit amount is normally kept aside, and only gets used in the event that the car is not received in the condition that it was taken in, with the exception of the fuel fee of course. Now, all of a sudden, the deposit fee is used to cover other costs, which I have supposedly incurred.