Where to file, lower, high court or CAT?

My father was government servant in DoT(now BsnL).He went missing on dated 23-10-95 and my grandfather lodged an FIR on 10-07-96, other was lodged by my mother on 16-01-97 and filed an application to GM,amritsar in the month of dec-97.As department said that it will take 7 years but when she went after 7 years then they said that they dont have any record of my father as department is now changed from DoT to BsnL(in the year of 2000). As someone suggested us to take up the case to BsnL.Again,my mother filed an application to General Manager of BsnL,amritsar on dated 16-06-15.They didnt rispond.I decided to write an application to the Hon.Prime Minister through Public Grievance Portal on dated 12-08-15.Finally they replied on dated 26-10-15.They mention in their reply that they not bear any acknowledge of recieving that application which my mother wrote them,we are approaching them after 20 years,they found the service book records of my father which said he is removed from the services on dated [deleted] even they not able to find the personnel file of my father,they issued charge sheet under rule 14 CCS (CCA) rules 1965. My grandfather was retired from the above department but unfortunately he died in 1999.My mother is ungraduate and there was no one to help so she dont know about anything.I got to knew this so started in again.I obtained the non-traceable certificate from the police and by filed an civil suit for death declaration but i dont know what next? Kindly help us with guidance.