What can i do to get my money back?

[Mebin]

Hi recently i tried to buy some poker chips on Zynga poker through facebook,(72mill). How ever after i entered my card details i got a pop up saying " that there is some problem, try again later or contact your branch". So i though the money has not been taken, Because facebook is american and i am from UK there was some issue. Next day i found out that £17.61 was taken from my bank account by facebook and i have not received any chips from the game, and when i checked my purchase history on facebook and it was empty. So i have been charged for nothing? Can i claim a charge back or is this fraud or what can i do to get my money back. I am confused on what to do.

Thanks
The transaction was not made cuase my purchase history is empty. the price for the 72mil was £17.16 which has been taken. what do i tell my bank. i want to report a fraud? or i didnt authorise this.?