Dakshin Haryana Bijli Vitran Nigam Limited - Undue demand of amount

I am having Dakshin Haryana Bijli Vitran Nigam Limited (DHBVN) electricity connection, bearing Meter No. **********.
I received a memo-*** dated **-**-**** through DHBVN which was delivered to me on **-**-**** which said "we have charged less bill charges in your account in the period */**** to *-****, therefore you are required to pay the dues amount of the last year i.e. around Rs. **,***/-."
I want to state that I am a responsible citizen and always clear my electricity dues timely and even much before the last/due date and have never been charged late fees for paying the electricity bills.
Since I have paid all the electricity dues as per the electricity bills as raised by DHBVN and no outstanding whatsoever is pending on me or in my account. The authorities never at that time raised any concerns and accepted all the payments. Now through this memo they are asking for the payments which are totally unjustified.
Regularly the meter readings were taken by DHBVN officers and on that basis the electricity bills were issued and to which I paid them without a single miss. Neither I am at any fault nor I did any wrong then why should I suffer/pay this illogical amount.
Since I regularly paid all my dues regularly on the basis of the electricity bills raised by the DHBVN therefore there is no question of any outstanding or less billing in my account. When I went to the concerned SDO office, he said I don't know you have to pay this amount without delay.
The allegations/demand levelled in the memo-***, dated **-**-**** are not valid. Therefore I sincerely request to lodge my grievance and praying for the resolution by cancelling the memo and issuing the NOC in that regard.