Bike sale Fraud and forgery of papers through olx

I bought a KA registered bike which was in mumbai through a ad seen on olx.the seller gave me the noc as the bike was on finance stating that he has cleared the loan.also as a proof i took his aadhar card xerox,original bike rc,signature on form (29,30),written proof that he is selling me the bike with no cases or dues left.also i took the picture of him with his bike.the payment was done through phone pe and account transfer.while transeferring i came to know the bike has loan on it(full amount as he has never paid a single ruppee).ow they have blocked me on whatsapp and call. i went to mumbai to register fir but police personnel is shouting on me you should have checked the papers and not registering the case.just they gave me a xerox copy of my complain with stamp.ow they are saying go to civil court and file a case.we cant do anything.if we will get notice from civil court then only we will arrest him.i have also provided the seller original aadhar no,office details,etc.