Land issue

Sir, My grand father has a land long back and which is acquired a person in bulk from all the farmers. later he died and he doesn't have any legal heirs so all farmers are acquired their land back and started cultivation. As no one has documents so farmers started selling their land around 11 year ago. We sold the land in terms of bits and while selling one of the bit , one farmer who is educated said that this bit was already sold by the person who acquired land in bulk. so we stopped selling that bit. One of my relatives who stays near to that bit consulted us and said they want buy that bit. we said to them this was already sold we are keeping this bit in hold. after 3 years no body came for that bit of land. again my relatives approached us and please sell that land to us suppose if any one comes for that bit you can revert the money what ever i paid. around 11 or 12 year later , recently one retried CI came and claiming that land belongs to him. As my father is not educated he don't understand what is there in the document. my father said this is already sold. if you have proper document then come to us. CI approached the narsipatnam police station. SI called my father. My father went to police station. they are consistently insisting on my father and asked my father to sign in document. as my father is not educated he signed and came back from police station (i am assuming this is kind of threatening ). What we sold is having different number than what the CI land document but in the map both pointing to same place. CI went there and evacuated the my relatives. Now my relatives came to us and asking for the present rate of money or same amount of land they have changed their words what they have promised us earlier. Can you please suggest, Thanks in advance.