Mercedes Authorised Panel Beaters are Useless

On the 10 July I took my car into renew it sandton for panel beating. On the 4th August they called to say that the car was ready for collection. However when my husband went to collect the car he noticed that they had burned the car during polishing and that there was now additional scratches on the car. He refused to accept the car in this condition. They promised to fix all the mistakes. We were contacted again on the 12th August. My husband went to collect on the 13th and yet again there were scratches and spots where the car had been polished to the metal! Unfortunately as he had returned the rental he had to take the car but was promised that renew it would provide a courtesy car and collect the car for repairs yet again! They were meant to collect the car on the 24th but we were not contacted and no body came to collect. Everytime we call renew it and speak to a different person they pretend that they have no idea what was promised by someone else. The Renew it branches are the only Mercedes authorized panel beaters in Johannesburg and its clear from their workmanship that they don't know anything about panel beating. Is this the quality that Mercedes Benz SA are willing to accept? Please review your standards for accepting Renew it as authorized panel beaters.