Need Suggestion On Potential Fraud

Hi, I have sold my Activa from online site to a unknown person, he give me his voter ID and paid all amount. Also he asked me sign form 29-30. And take RC as well. But now his phone is switched off and he is not transferring RC. Also I check online the Id he provided seems fake voter ID. Pls suggest what I should do, also police is not taking my complaint.