Momentum insure ,not to be trusted as Ur preferred insurer

I had an incident where I drove into an pothole/ drain . This was caused by the road department I guess where they worked on the road by didn't cover the hole properly , my car was damaged due to this .my car was manually assessed by their guys and was being bill R5600 for a replacement tyre (which was the incorrect size) , wheel alignment and repairs to one rims . I rejected that bill cause I knew it was to much and took the vehicle to a Tyre company who showed me the faults which momentum assessors didn't find . I finally get the quote to momentum and was rejected as , I was told that my car was old and I need to use replacement parts .now I own a Opel Corsa opc and u don't get replacement parts for this car. I tried explaining this to them but I guess their assessors have no idea about car . So I then go back to the tyre company for a discounted price as my first quote with original parts was to high , after crying n pleading with them ,they dropped my quote under one condition,that I pay the balance on a monthly basis, now I'm still have issues trying to get my claim amount Paid to me . It's been about a month n still having the run around . I now have to get reports to prove damages to my vehicle.why do we actually pay for insurance when we have to do all the work for them n still pay high premiums.its a total rep off ,so guys do Ur homework before choicing momentum insure .my first claim in 4 year and I'm having issues.