Increasing Premiums and excess

After many years of dealing with Santam, I have just realized that my vehicle has dropped to less than half the value of purchase price. I originally chose an excess of R3000.00 and paid more on monthly installments. Since 2020 my excess has increased to R5000.00 and monthly installments have increased considerably. Given the age of the vehicle, one should pay lower amounts due to the depreciation of the vehicle. My vehicle was insured for around 500k and the market value is now 250k. Why am I still paying for a 500k vehicle when I will only get 250k? I did call through and there’s nothing they can do about this even after I told them that it is not worth paying so much for a car that lost its value.