Insurance companies

I have a problem with santam car insurance company...I had an accident on end of July and reported the matter immediately and my car went to panelbeaters for repairs ..the insurance gave the panelbeaters the go ahead for repairs and the price to fix the car was R150 000 but after the panelbeaters stripped the car it had some additional parts which the cost rose from R150 000 to R190 000 so suddenly the insurance opted for a write off of which I didn't agree with so I told them that i will pay for additional parts myself but still they don't agree to...they want to pay the bank and take the car for auction because of it is still in good condition...can I please have some help on the matter