In-app purchases are generally non-refundable, but on occasion there can be exceptions.
As the transaction process is handled by Google (for Android devices) and by Apple (for iOS devices), you need to contact them directly with your refund request.
For Apple (iOS) devices:
- Visit Apple support
- Enter the Contact iTunes store support > Purchases, billing and redemption
- Select the option that best fits your request
For Google (Android) devices:
- Visit Google Support
- Select the Contact Us button
- Select the option that best fits your request