India Property Online — Brokerage not being paid

I had sold 3 b 706 flat for sunteck india limited for which they are not paying the brokerage. They now say that it's direct walk on. Where as o have all the proofs that it's thru me. The customer himself has sent an email to them that it is thru channel partner. I had sent a whatsapp message to the sales manager stating that i was bringing the client. I have the message as a proof. Now they are trying to send a corrupt file which is not opening. I have it with me. After everything is done now they are refusing to release payment. Can you help me to get the brokerage?