Tamil Nadu Electricity Board [TNEB] — shortfall in misc. collection for non defaulter

Address: 600048

For my consumer ([protected]), i have seen 2 entries for shortfall in misc. Collection with charge rs are 620 & 1230 on 30th july 2019. When i checked reason on online, this charges comes only if any pending arrears or any defaulter. But i always pay my bill within 3-4 days from bill generation date for past 3 years. I have raised complaint ([protected]) on 11th sept 2019 and till now no response even that went to 2nd level escalation. Even i did approached local eb office and they are telling this is advance amount but for advance amount entry should be "deposit" and usually advance amount get collected if my usage is very heavy then normal but that is not the case for me.
As i didnt get much info from eb office, so i check contact online & found whatsapp number. When i am trying to chat there is not even single response. Whatsapp is just dummy.
I am more interested to know why this charges added to my consumer that too twice and also why i am getting charged for that need clear details. Please assist.