Refund for "old damages" deduction on a written off car

My Car was involved in an accident in January where it was written off. To me the damage wasnt major because i was able to drive the car to the police station after the accident. The damaged areas where the right front and back door , which need to be replaced. So Discovery wrote the car off, settled the bank and made payment into my account for what was left. As part of the vehicle assessment, an amount of 6675 was deducted for "old damages" on the car - not sure why this was done because the car was written off.

I then proceeded to asking the consultant to purchase the car back (salvage) from them, as I had previously said that the car could be fixed. The Discovery guys referred me to Auction Nation, who were then then owners of the car, and I spoke to them. After some back and forth negotiating , i managed to buy the Car back from them for 73000 (which was expensive because it was explained to me the salvage of a written off car is 30-40 % of the retail value (R167 000). None the less the transaction happened and I got my car back in the state they had taken it.

I then contacted TIB and Discovery for the money they took for "old damages", I was told that they not willing to pay it back because I had accepted the amount they settled with. Which was true but that acceptance was on the basis of them keeping the car. It would make sense for them to refuse to pay me on the basis that the "old damages" have been repaired, but they haven't. I still want my refund because i have fixed the car including the "old damages" with my money.

A brief history of my insurance...

I took out insurance for my car (Audi A3) in 2014 with TIB insurance brokers. At that time TIB was underwritten by Hollard, & around 2 years later TIB moves its client to discovery insure. In that move we were assured that this was beneficial as it came with lower access, in an event of an accident but everything else with remain that same - including the clause of the previous contract as well as the monthly premiums.