Momentum Insurance unacceptable service

I have been with Momentum/Alexander Forbs for 30 years. My vehicle Mercedes SLK has not had a claim since new. This last month I put in a claim for a small repair that needed to be done after I damaged it on the pavement that had been dug up by the Johannesburg Water who have not closed the site . I put in a claim and was sent to their assessor in NET Assess Kyalami. He did a quick look at the vehicle without putting it on a lift (did a small jack up on a very uneven surface and tried to stick his head under the car to see damage) I waited two weeks for a reply from Johanna at momentum. Eventually I called and she promised to get to the assessor and give me feedback. She did not call back. I phoned her two days later and she said she would send me an email with the assessor's report. The report stated that the damage repair cost was R9009.86 and I was directed to a C grade repairer. My vehicles have always been repaired by our faithful Auto Body repairer and I requested that they use MF Auto Body for the repairs. I was told that because my car was out of warranty it has to go to a repairer who fits secondhand parts. I indicated that my vehicle was in pristine condition, and I was not happy about a second-class repair and that the quote did not include the full damage. I took the vehicle to MF Auto Body and got their assessor to give me an assessment for the damage. This assessment was emailed to the claims manager at Momentum asking for an explanation as to why the original assessor did not give a full assessment to date they have not responded. I need to have my vehicle repaired urgently and have requested answers from Johanna who promises to call back. Tried a few times to call her but without success.