IDBI Bank — idbi deep discount bond series 1-1992

I had invested in one deep discount bond series 1 of 1992 series under regd folio no dd 00502152, certificate no 00600503, distinctive no[protected] with issue price rs 2700 and face value rs 100, 000 which is matured on 31st march 2017. I have sent an email and reminders to idbi nominated registrar (Einward. [protected]@karvy.com) but not getting any response.
In the above circumstances, what is to be done & whom to be contacted for getting our money back.
Best regards.