Defective material supplied by cheating

I was shown correct sample of a chemical, but supplied wrong material in a sealed drum by a south Indian supplier at New Delhi. He took cash in pretext of sending the invoice once he reaches back to his office in South India. But, he never gave any written proof, and lied all along. I have been cheated by this man. His phone no. is working and talks also. But never comes in front and won't tell where he is in Delhi when he is visiting. His earlier mentioned addresses seem to be false too. I have recordings of his conversations with me in my mobile. Now, I have also heard of similar complaints from many other such buyers of this chemical. I tried to complain this to Police. They first took my complaint and also gave me a receipt on my copy. Now the SHO is not taking any action on the matter and says that I do not have any proof !? I told him that I have been cheated. I have voice recordings on my mobile of conversations with him. I requested police to track his location by his active mobile no.and arrest him to know the truth and recovery. But police is not moving at all !? Since, i do not have any direct documentary proof of this deal, can i not take any action against this cheat !?