Bangalore Water Supply & Sewerage Board [Bwssb] — incorrect water bill

Address: Dno 97 , 5th cross Talakavery layout Basavanagar, 560037

Last month our water bill is 3731 rupees & i paid the bill on 7th july & for august bill it says that i did not paid my last month bill which is 1571 rupees which is not at all fair.
Our rr no : e-340207
How can you say that i had not paid the bill when i actually paid it and that too the amount which i paid is more for last month bill. Please solve this issue.