INSUREAFRICA - clients comes last?

I have an motor plan and a top-up on the motor plan for my 2014 GWM H6. The Vehicle overheated and according to GWM Richards Bay workshop manager he don't know why as the oil and water was OK all though there was some water in the oil. They send the vehicle to Engineering and according to the engineering, that happened because the OIL Cooler was leaking. I know there was no oil or water leaks on my vehicle and can prove it. When I spoke to GWM they said the leak was internal - into the engine. According to me, that means because of this failure, water leaked into the oil, causing lubrication problem, causing overheating. Thus the engine got hot. total cost to repair is R30,000 and INSURE AFRICA only want to pay at R7000 on the policy (plus R5000 for the top up). They do not want to pay the R25000 for Engine failure as they said the engine failed because of overheating. I say that the engine got hot because of engine failure (Oil cooler). Except from that, INSURE AFRICA never phones me back - seems they thinik that there word is final and they do not have to wate time talking to the client. Miskiet Engineering don not want to give me the original report (They say that GWM is their client and they don't have to talk to me). GWM send their own report to insureafrica that may or may not be correct and I am forced to pay 18000 out of my own pocket.