Sardar Sarovar Narmada Nigam [SSNNL] — how can I convert the bonds in money which has been promised to my father at the time of issuing the bonds.

Address:

Durg, Chhattisgarh, 490006

I do have a couple of bonds with me which my father has purchased, so I would like to know whether I can convert that into cash none of the numbers which is mentioned on the website is working that's understandable though because we are in India and I know very how efficient and cust centric govt is in India.I guess India is probably the only country in the world where govt bonds can also be fake or fraudulent if not then why no one is receiving call on any of the numbers mentioned on the website I wish I am wrong and I will get my money which has been promised so, please help me with it.