Bad customer service and no feedback

My car was ****** and then recovered more than 4 months ago. Earlier in the year the car was assessed for damages because the person who stole the car had hit a wall and ran away leaving the car. In March the car was taken to panel beaters by the Oakhurst Insurance for repairs. I clearly ask Vuysile to take the car for an AA test after the repairs, and he said there was no need for that considering the damages on the car. Last week I got a call from the panel beaters informing me that there's noise coming from the gear box and it must be replaced, he then said my insurance doesn't want to pay for that damage. I contacted Vuyisile to inquire about this, and to remind him that he said if I'm not happy about the repairs I must take it up with him, he then told me that the gearbox damage was not related to the accident according to the assessor. I've been asking him to prove to me that the gearbox noise is not related to the accident, and he has since disappeared without giving me any proof. How did the assessor come to the conclusion that the noise is not related to the accident? If the above can't be proven, then the gearbox repairs must be paid for. CAN I PLEASE GET ANSWERS HERE?