Refunds are handled directly by Apple since they are the only ones that can access your purchases to refund. To request a refund from Apple, please follow these steps:
  1. Go to Apple's problem reports page: http://reportaproblem.apple.com;
  2. Login with your Apple ID;
  3. Select the appropriate tab: Apps;
  4. Find the purchase you want refunded;
  5. Click on “Report a Problem”;
  6. Select the reason why you are requesting the refund;
  7. Fill in the description box with the explanation;
  8. Click on “Submit”.
Keep in mind that you can easily manage the ability to make in-app purchases or disable in-app purchases entirely through your device’s general settings. The instructions can be found here.