Consumer Redressal

I ask to fill up full the tank of my Honda city car at a filling station. The capacity of Car is 42 ltrs. however the person claimed to fill 45 ltrs in my car as the meter was showing 45 ltrs. I argued with him that this is not possible but insisted me to pay the full amount. he also gave me the slip of 45 ltrs. Kindly advice me how to lodge complaint in consumer forum.