Freedom fighter assignment land

Respected Advocates.... Requesting you to suggest a feasible solution for the below mentioned grievance My grand father was assigned 10 acres of banjar land under freedom fighter scheme during 1977-78. From 1980 onwards other people have started agriculture on our land till 2009 mentioned in the pahanies. Neither my grandfather(died prior to 2005) nor my father sold the assignment land to others till now. As per the pahanies from 1979 to 2009 the pattadar was my grandfather, the occupants were others mentioned in the pahanies. However suddenly in 2010 the pattadar name was changed to third person (.i.e. not my grandfather nor the person's who took up the agricultural activity all these years). Till 2008 there was no mention of sale in pahani copies, however the 2009 pahani copy reveals that the pattadar was my grandfather and occupants were same but showing "Occupants purchased our land". And now new third person has emerged in pahanies from 2010 to 2017 showing as they purchased land from the occupants. The patta and passbook was transferred from my grandfather name to third parties without our knowledge and involvement in 2010. 1978 to 2009--- grandfather as pattadar 2010 to 2017--- Third person as pattadar 2009 pahani showing as sale from grandfather to occupants, pattadar being my grandfather. 2010 pahani revealing sale from occupants to third person. In between there was no change of patta name from my grandfather name to the second party .i.e. occupants Presently, now the pahani is showing Third person as the pattadar and occupant. Requesting to suggest whom to approach (revenue, police officials) legally so as to get back our land.....