Getting consistent Water Bill of Rs.800 from KWA for the house which is lying vacant for the last 1 year.

My family got a second house which is lying vacant for the last 1year.For the last few times, I am getting a water bill for Rs.800 with no variation in meter reading.They said if the meter reading is exactly the same, they would charge the average of previous reading, something like that...Since I am new to this, I fell for it...Last time they said if there is a few difference in meter reading, water bill will be close to minimum...I did that & there's 4 units difference in the reading.I thought it would be enough but they scammed me again...Got exactly the same bill again... Not sure how to deal with that...My last complaint was not taken into consideration... What should I do to solve this & get refunded for all the overly charged bills?