Need assistance as to how to proceed further to get pani done.

Hi All, I would appreciate your help and guidance in advance. here is my current situation and this is subjected to Bangalore judiciary. My ancestor have purchased a 3 acres (grand mother) revenue agriculture land during the year 1970 by making full payment and got the document registered at sub-registrar office Bangalore south. My grandmother passed away in the year 1980 and also my grandfather is no more. We are now grand children's and our parents are the successors of this property. 1. Unfortunately the pani and katha is not been done till now with respect of the above property and we have all original registered document. 2. EC shows that the property is sold and registered in my grandmothers name, however the Pani is still in the name of the seller and also the position of the property. Please guide how do we need to proceed further with the documentation and to take the position under our control.