Huf bank operation on the demise of karta

Hi My father had opened an HUF bank account with one of the nationalised bank. Lately he passed away & I approached the bank branch manager to make the karta so I can operate the account. This gentlemen refused that the HUF needs to be closed & cant be operated anymore. Father (karta of the HUF) Mother - coparcener Sister - coparcener ( elder & married) Son - coparcener (major but younger to sister) In my case who can become the karta. How should I make the branch manager understand that HUF account can be operated even after the death of karta. Which competent authority should I approach. Please advise & guide. Thank you.