Service levels are terrible waiting 6 months

A discovery client reversed onto my car which was parked in a parking lot, the client admitted he was wrong and advised his insurance will cover, but up to today i am battling in getting my damages repaired. I phone/email no response on time, i have comp**** with information relating to the incident, i took my vehicle to their appointed assessor, only for discovery to provide me with an incorrect assessment, the assessment does not match with original assessment of where they sent me to, they sent me a different quote with half the value,they have not added some damages saying old damages(car is new), i called the people who done the assessment they said that not what they supp****,i even supp**** an assessment report done 2 weeks prior the accident saying car has no damages, and now they saying their client has a different story of the accident but i spoke to the client and he says he hasn't, i made them phone the client and now apparently the client story matches mine. I am so fed up as i still have no response from them, even the manger of the dept is unresponsive. Its just back and forth. i am just asking for my car to be repaired, is this so hard to do?please help?