HDFC Bank — Negative balance in my account

My salary account (In hdfc bank) was created in my first company, so once I left the company. Now my salary account in hdfc bank has been converted to savings account (Without informing me or warning me). After that i never logged in to my account through net banking and i do not have a debit card (Lost in 2 years back and I never requested for a new one) I visited to Bangalore branch to close my account as I did not want to use the account and they said that there is a negative balance of more then 5K and this can only be waived off by the home branch in Indore I tried multiple support numbers but I am not able to get in touch with them. I request you to please take action against this bank.. They have no right what so ever to do whatever they want without informing the customer and I want my account closed ASAP.