Contact your bank/credit card company & ask to be put in contact with their fraud department. Ask to have the transaction cancelled b/c it was a scam. Also, you can report that site you paid the money to at the top of the page here Known Scam Sites (click on link) And see if you can identify which site you paid your money to.

It may also be worth cancelling your C/Card as that scam site might charge you monthly or whatever.

More tips here Membership? - **WARNING** - Download p2p Clients ONLY Thru Official Sites (click on link)