If my child takes the money that I left on the desk, goes to the shop, buys candies and eats them...can I go to the bank and ask them to give back my crisp bills? Or maybe go to the candy store and whine there?
You went to the candy store with your child and paid via CC. The candy store saved your CC by default, and due to deceptive UX, made it difficult to figure out that you needed to opt-out of the saved CC.
The next day, your child was walking past the candy store and the candy seller runs outside and says, "hey kid, you want this candy? its super good and you can have it for 5 dollars! just take it, its yours!"
kid takes candy, you get charged $5.
and in reality, even the "you can have it for 5 dollars" part is generous. facebook did not require the game developers to make it obvious when things cost real money or not.