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

Sir,
I'm the owner of the house no.28-29/4, 8th Cross, Maruthinagar, Madiwala-560068
My parents were living in the house untill 13 june2020. Due to the increased covid cases and old age they have been rellocated to senior citizens care center. Since then the house has been locked and no water has been used supplied by the Bwssb.
I've been paying the minimum charges charged by bwssb.(through ECS )
But this month we are given a bill of Rs 12335.00(Rs Twelve thousand three hundred and thirty five)
On enquring at bwss office BTM layout I did not get a convincing answer.
I cannot understand how bwssb can charge for the service not used.
Please look into the matters and rectify the bill at the earliest
Thank you sir
Sincerely yours
Charlotte Lobo
[protected]@gmail.com