Bharat Sanchar Nigam [BSNL] — lost my handset along with my bsnl sim card

I have lost my bsnl sim card and customer care is not helping at all to deactivate the number.
I want to block my number [protected].
Bsnl customer care is redirecting from one to another from past 2 hours and no help. It is really irresponsible. No way to file a complain.. No way to block the sim, which cause a security issue.
It is customer cares duty to help the people in this case, but either numbers are not working or they are not helping.
It is highly important for a customers service to listen to people’s complaint atleast when the person is saying it is an emergency