Unacceptable, shoddy service from Discovery

I had an accident in early March 2018, Discovery authorised my claim approximately two weeks later and I was given a courtesy car for 30 days. The 30 days ended mid April and my vehicle was not ready as the panel beaters we still working on it. The panel beaters called me on the 26th of April to collect my vehicle as they had completed the repairs. A few hours later I informed them that I wouldn't be able to collect my car on that day (26 April) but rather will do so on Monday 30 April, they emailed me to inform me that their work was quality failed by Discovery therefore I should wait for them to inform me what time to come on Monday. The panel beaters did not call on the 30th, I assumed they were still working on my vehicle. After two weeks of no word from them I contacted Discovery on 11 May regarding the progress on my vehicle. As per their (Discovery) system notes i received my vehicle on the 1st of May! After informing them that this information is incorrect they contacted the panel beaters who then told Discovery that Net Assess has declined to authorise the additional work required on my vehicle and that my vehicle was taken to Audi centre Northcliff for assessment. At this stage I am not told what is wrong with my vehicle, a few days later after pushing Net Assess and the panel beaters for a response, they come back and say that my vehicle has no power and Audi has attributed this what they call a soot filter that needs to be replaced. Net Assess then states and concludes that this is a wear and tear issue not related to the accident. I then spoke to the service adviser who was attending to my vehicle as I needed it to be thoroughly explained to me. This gentleman explained to me that my vehicle is currently not drive able as it has no power. He further said that the soot filter needs to be replaced. He gave me a more technical understanding of the diagnosis. He said that it is possible that due to the accident this has now occurred. My issue is that I do not understand why Net Assess has dismissed this as a wear and tear issue given that I was driving my vehicle on the day of the accident. Had this been a preexisting issue my car would have not been drive able on the day of the accident and prior to that. I sent an email to Discovery on 24 May with this query and nobody responded. I then called them on the 28th and I was told that the vehicle repair management department is supposed to respond and make a decision. I insisted on speaking to someone in that department who then told me that since Net Assess has rejected the additional work required, the claim is to be referred back to the claims department for a management decision. The person I spoke to from vehicle repair management department, spoke to the claims department and said a specific person is discussing the matter with his team leader and he would get back to me. This was on 28 May. On the 31st I call Discovery and I was told that the same specific person will discuss the matter with his team leader and call me back within 5 minutes. Nobody called me, I phoned Discovery AGAIN on 4 June and I was told that the specific person and his team leader are not in the office. I insisted on getting assistance from someone else because surely Discovery is not run by two people. I was then assured that one of the other team leaders will call me back by the end of business on the 4th of June. Today is the 5th of June and STILL NO WORD FROM Discovery!!!