My car met with an accident which was not my fault. I claimed the insurance through the the other party's insurance company. When my car was under repair they provided me with a rental car. The rental firm gave me a mini car due to non-availability. Once my car got repaired, the rental firm say that the insurance company paid only for a standard rental car price and not for a mini-van and charged me the additional amount. I tried to contact the insurance company but they are not responding. How do I complain against the insurance company and rental firm.