Icici Direct — Deducted 826Rs though it was said to be lifetime free demat account

I have opened my demat account with icicidirect during 2017 and bank representative told during that time "this demat account will be lifetime free and no AMC/other charges will be charged in future as I am having salary account in the bank".
Now on 28-Sep-21, they have auto deducted INR 826 from my savings account as DP charge. Now, this is a case of clear misinformation and cheating from bank's side.
I need proper justification and also refund of my money.
I am a 10+ years old customer to the bank but they have lost all trust now.