Resignation not being accepted by the psu bank

I am a PSU bank employee. I resigned from the bank during march 2020 giving 3 months notice period. My last day was 02.06.2020. However on 01.06.2020, my HRM informed me that one vigilance case is pending against me in some other Circle Office and hence my resignation could not be accepted. Subsequently all the enquiry process was completed within a month. However I was charged the punishment which states as follows :"reduction to a lower stage in time scale of pay by one stage for a period of one year." the concerned persons told me that it won't affect the resignation. It will only affect the amount of PL encashment. I once again requested my HRM to proceed with my resignation request. However, its now been almost 2 weeks, they have still not relieved me. They are orally telling me that the punishment is for one year and that I have to serve the bank for 1 year. Also they are not giving anything in writing. Please guide me in this matter