HDFC Bank — Minimum balance due

Today when i checked my bank statement 5, 508 rupees was deducted from my account with multiple transactions for not maintaining minimum balance. I started this account as salary account and when i changed my company i changed my bank account as well and nobody from your bank or anyone informed me that if we don't use salary account for a long time the account will be automatically changed to savings account. When my account was changed to savings account i didn't get any notifications via call or email. Now i changed my salary account back to hdfc And now i was being charged 5, 500 for not maintaining minimum balance without any notifications or any debit message nothing how come the bank have a right to debit this much amount from my account without any notifications. I want my money bank. Atleast the bank should notify the customers about this change and i wasn't aware about this. Atleast the bank should have informed me about all this, i want my money back. This is not my mistake.