Claim rejected on assumptions and no facts considered

These invite me to take up insurance with them since they are financing my car; two months later I get into an accident and they decide to reject my claim claiming I was negligent when driving and resulted into a crash. They say they hire some expect to re-construct the accident since to determine speed. Firstly, they go to the scene a month later after the accident had happened; the time and conditions of the weather were not even considered; they are giving assumptions that because there is not speed limit signs in the area I was speeding that say normally a person should have been driving at a certain in that area of accident. Absolutely ignoring any of the fact that led to the accident and they conclude that I was driving on an excessive speed.