how exactly do i report a stolen iphone with a serial number? when iphone is not activated please help! all i got is the serial number for it

Please help! i was scammed by someone on Ebay with a purchase of an iphone and now they have the phone in their possesion and never paid me back, Ebay and Paypal refuse to do anything due to the mail tracking showing its on its way( this is over 2 months now) i dont have my phone and i am short of money due to the scammer. All i have is the serial number to the phone and the iphone was not activated on it. Does anyone have any suggestions or ideas?