Reliving letter not giving by bank and warning to terminate

I was working in a private bank. I have left my job from there and there was a notice period of 90 days on which I could not complete it. I had informed them 30 days ago and completing serving 30 days notice period and ready to pay shortfall amount of rest 60 days. but bank not giving my reliving latter. many times I am request and mark mails to bank. kindly help.