Sale deed fraud with my father.

My father bought land but land owner cheated us. After making payment all of us went registrar office there was shop where registry draft created. After the reading draft we are confirm for online registry but that moment land owner refuse to registry and told us he have missing document so he will do registry next day. After to days we are reached registry shop they all told us your father are DIVYANG, he cant walk and you all study the draft previous day so let him registrar office which was far approx 100 meeter. We waiting registrar office and this time they changed registry draft and send online and in registrar office we all signed but we did not know about this change. We got to know after 1 month when wee see registry and first day written draft because they sent that draft on that day. I have mail as a proof and call recordinh and video recording of registry writer who admitted that change was make without our consent. Please guide we borrowed 10 laksh from bank and paid 16.50000 for land owner. 11 lack from bank and 5.5 laks cash. We want to cancel sale deed and want our money back. We registerd land on 2018. Police refused to fir.