Tamil Nadu Electricity Board (TNEB) — meter reading not taken, but higher payment was asked based on previous month

Address:

Chennai, Tamil Nadu, 600119

The tamilnadu electricity board, chennai south [selaiyur], they are not taken any consumption reading for the past month, suddenly yesterday i received bill of rs. 2704/- they calculated amount based on the last time amount which i already paid & the same needs to pay this time too.
More-ever in my e-bill, previous reading showing 1420 kwh and current reading also showing 1420 and i don't know on what basis they assessed consumed units 640 units.
I regularly monitor my meter reading it was not more than 450 units this month.