Offer Letter Withdrawn on the date of joining

This is Ayanjyoti Das. I have been a pharma sales professional for last 12 years. Due to some family health issues I had to leave my job in July 2016. After that I was busy in taking care of my father's health and unable to appear for any interviews for the next job. Subsequently my father's health deteriorated and he died on 7th August. Then onward I started searching for the next job and I got an interview invitation from Lundbeck India Private Limited, HM towers,No 58 1st Floor Brigade road , Bangalore -5600025, as an ASM Kolkata. I have cracked the interview and they sent me the offer letter on 30th August. My joining date was 1st of September. I was very happy as it was a second life for me after a dangerous phase of my life. But all of a sudden in the morning of joining they called me up and said, "We are not going to continue with you and your Offer Letter is withdrawn with immediate effect". I was shocked and repeatedly asked for the reason why the have done so. I have not hidden a single thing about me and I expressed my current situation and requirement for an immediate job to run my family. End of the day they said to me that,"You have communicated to another probable candidate about company while the selection procedure was going on. That person was unknown to you and you have searched for his profile on SNS(FB). This is unethical and we cannot continue with a person like you". I was stunned, then also I pleaded like anything that it was completely unintended and I didnt mean anything harmful about the organisation. But they denied to listen anything from me and stick to there decision. Actually what happened is, the company sent me a communication asking for my testimonials on 26th August, 4 days prior to the offer letter. Incidentally they have sent that mail in reply to some other candidate's mail. I have sent my documents to the company and started searching for that profile on Facebook just for curiosity purpose. I have found him and chatted few words regarding our candidatures and asked him if he also got the same communication or not. It was ended like this before my joining. Now on 31st August night this man has sent this communication to the company and asked them how they can send ones mail to another person. He was worried for his professional secrecy. I am jobless for last two months and I am the elder son of my parents, with my wife, daughter and mother. I have to now head the family after my father's untimely death but I am unable to contribute a single penny for my family. I have communicated to all my friends, relatives and family well wishers who were worried for my future. With all the good wishes and thanks I was going to join a new job and suddenly entire world became dark for me and that too, without my knowledge. I have lost all my social status and my dignity after this cruel behavior of the company. I know, they are not going to give my dignity back, but I want to know, is there a provision to file a case of Defamation against the company for the compensation of my social respect and dignity ? I can provide all the documents to support my complaint. Kindly help, I am helpless.