First of all, a signature on plain paper confirming goods were received may not hold much weight in the court of law. You may report the matter to the police but I believe you may need to seek legal assistance in your case and this may cost you a bit of time and money. Sad to say, but it is a bitter experience you have had and as it is commonly said, "Leave it to Allah," I would suggest the same. There are all sorts of crooks around in the world and it appears that the people who cheated you, knew their game well.