Charged old damages on write off

I was involved in an accident and filed a claim. I received notification that my vehicle has been written off by the insurance company. Then I received the loss agreement with the settlement amount, and to my astonishment, R6500.00 was deducted for old damages. There was a minor dent comparable to a quarter of a finger, and the insurance inspected my vehicle and found that damage prior to joining the insurance. According to my understanding, the premium was charged based on the state of my car; why am I being charged for this damage now? I am told i should contact the assessor, how is the assessor going to help me, beacuse he was not there when i first took the insurance with PSG. This is daylight *******