We have lived in our house since 2002 and it has recently come to light that Severn Trent have been overcharging us. Our ground water doesn't run into the sewers as we thought and had been charged for but soaks away. They have refunded us for the last three years, around £280, but are refusing to backdate any further. Do I have any grounds to complain to ofwat? Any help would be appreciated. Thanks