How to get a refund

First, make sure that you did not inadvertently make an in-app purchase. Many apps, particularly games, are free for the base game but charge for additional features such as levels, "coins" and other such add-ons. Check your Purchase History to see if that reminds you as to what you might have purchased:

http://support.apple.com/kb/HT2727

If you find that these were in-app purchases, to prevent this from happening again, turn off "In App purchases" in the Restrictions settings on your device. For more information, see:

http://support.apple.com/kb/HT4213

As to a refund, that's not automatic since the terms of sale for the iTunes Store state that all sales are final. You can contact the iTunes Store, explain the reason for your request, and ask, though:

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

They're usually pretty lenient in the case of inadvertent purchases, but there are no guarantees.

If the charges are not in-app purchases that you made and forgot but the charges do appear in your Purchase History, contact the iTunes Store and let them know. You should also immediately change your password for your Apple ID. If the charges don't appear in your Purchase History, they were probably fake charges made directly to your credit card, and your card issuer will need to handle those.

Regards.