Bangalore Water Supply & Sewerage Board [Bwssb] — Bill amount paid but not accounted in bwssb record

Address: HSR layout, 3rd sector, Bangaluru 560102

Sir, our water bill normally around ₹ 800 to 1000. But in March 2022 the bill amount was 5484. When we enquire in office they said as per audit some older bill ₹4816 not paid. We verified our record and founded the bwssb receipt for having paid an amount ₹ 4438 and we showed in office. They said give a copy of the receipt along with a letter. We did it but so for no action has been taken and the bill always show arrears. This months bill has come at ₹ 7057. With a arrears. Please help us to set right the bill.
Thanks