HDB Financial Services — Releasing letter

Address: Kolkata,Delhi

I have worked hdb from 2015 April to 2015 October as a tellecalling officer, My Em Id-HDB32766.due to some reason i left this job on november first week, I have informed my Supervisor Shabnam khatoon regarding resignation but she refused to release without serving 3 months notice period.but i was not able to continue my job on that time after a lot of request she taken a resignation letter but not provide any resignation receiving copy..now i want my release letter..tried to connect to hdb through twitter, local office, but no communication or response received..please help