In most cases, all transactions in the App Store are final. For a problem with an App or in-app Purchase, the best approach is to contact the Developer of the app for a resolution. They cannot give you your money back, but if the in-app purchase is not functioning correctly they can help in many ways. You may also have an option in the game to Restore in-app purchases.
If you can't find or use your in-app purchases - Apple Support
Let us know the name of the app and we may be able to help with providing contact information. You can also rate the app in the App Store and write a review to let others know about your experience. Some developers are more responsive when they have a review that is viewable by others that would have a negative effect on their downloads.