You can try to fill a complaint toward the POLICE but as usual, they will say that they have more important cases to investigate.
unfortantly they can not give you personal info on someone else. I would def do your homework next time before you buy especially an iphone as there are a lot of fakes out there.
like @Cyber said you could go to the police and file a complaint but most likely wont do to much as they say they are busy.
maybe a suggestion would be is to try and resell it. I know there are ppl out there that will buy the fake ones. You wont get your $650 back but you might get it partially back.
^Did you not open it to go through the iPhone menu? Fakes are very easy to spot when going through the phone menu.
You can sell your fake iPhone 6 for 100$ on Kijiji.
Many buyers purchase fake phone just to have the same look as the original one.
HI. Someday Advice: Always buy Handsets from Respectable Merchants, Avoid Strangers, Or even Kijijii. This way, $$$ well spent is $$$ Well. Earned. This is an Unfortunate circumstance