Relieving letter

Hello sir/madam, I'm Sunil, I'm working in bank as br manager . Sir, currently I given resignation of current job by giving 1 month advance notice as per condition of appointment letter. After the notice period completed I was contact to our HR for a relive letter but they can't cooperate me. They are postponing to give relieve letter. They are saying that my resignation issue was pending, so they can't relieve me. In resignation notice I give reason that " I am sick, so I can't work in bank so I'm giving the resignation. " as per my resignation notice they give me letter that I want to check up from the selected doctor of bank , if report comes negative, if report proved that I am really sick than they sanctione my resignation other wise they will refuse my resignation. It was big problem in front of me that what I do? As per appointment letter I was given 1 month notice, in this notice period I work also sincerely, after 1month completed of notice period I am not going job. What I do?