In order to request a refund from Apple, you will need to contact them directly (only Apple can issue the refund). Here is how to submit a refund request:
1) Go to: https://getsupport.apple.com/
2) Click on these options in this order:
- Apps and Software
- iOS Apps
- App Store, iTunes Store & Music
- iTunes Store Account Billing
- Report a Problem (Report an issue with a recent iTunes Store, App Store, or Mac App Store purchase).
3) Log in to your Apple ID that was used to make the purchases.
4) Locate the purchase in the purchases list that you wish to have refunded. Click the refund button on the right. Apple will then process your refund request for your specified purchase.
If you're interested, you can turn off the option for future in-app purchases: On the iPad/iPhone/iPod touch devices, the restrictions preferences can be found under Settings > General > Restrictions > Allowed Content (In-App Purchases) OFF.