HDFC Bank — HDFC is keep charging AMB charges even after maintaining average balance 10K monthly

My account has been debited since long time (more than 6 months now) with Rs.531.00 for "AMB CHRG INCL ST & CESS" for without any prior intimation or alert.

I have never been communicated via Email or SMS for any such charges they introduced.

If they can send promotional emails and SMS to their customers then why can't they send an alert about a new charges they impose; so that customer can maintain the balance before it goes below the required amount.

This happening since long time with me and I was not aware. This is not acceptable at all. I don't know why HDFC is charging this much amount. I can see my monthly average balance 10K and above and still HDFC is charging 531..this is strange isn't it??. I need a help here to get refund my all debited amount. Kindly process the refund for all these debit transactions otherwise I have to CLOSE my account with HDFC Bank forever.