Cancellation of Sale Agreement by buyers due to party is fraud

Hi All, We have signed the sale agreement with the party who has taken the land with sale agreement with actual property owner. We have give 3.5 lakhs in agreement with third party after speaking to actual owner with agreement to pay remaining 11.5 in next one month and post bank loan will pay remaining 15 lakhs with overall money 30 lakhs property. However, third party requested us to pay early how much can be paid due to actual owner has marriage. Hence paid 2.5 lakhs and got that singed in the same agreement. As same person was helping us to apply for loan.., he requested to give the cheque with 9 lakhs on owner's name Naveen. After getting loan fo m our relatives, we managed to gave him cheque in the name of Naveen and no need of initials. But, this fruad has credited to different person name as Naveen S instead of Naveen P. He has not given any agreement for this cheque transaction as he said it has been submitted to bank ppl without any of our signs. When we asked there was no sign put on those. He is saying Bank manager will call you and get all your signatures and proceed further. However when we check with owner , he says he never received any cash or cheque so I won't put any sign for registeration. Please suggest how to proceed further and even this fruad works in BBMP office in Bangalore and have more local influence with political background.