how can i get my money back from an app i did not buy

http://www.apple.com/support/contact/

I Am a low income family man that doesn't do stupid stuff like this I didn't even know what was going on when I was in the store trying to buy food f my family and it was declined. I called my credit card company and that's when they told me to contact that company. i think it's a major scam that takes people's money