I was overcharged for the game on the Apple App Store.
We highly recommend that you get in touch with Apple’s support as they do not give app developers access to any tools to support customers experiencing issues with the App Store. We merely submit our games to the store while Apple handles their sale and distribution.
Because of that, we are unable to access billing details and process refunds.
Follow the steps described in the link below to request a refund directly from Apple:
https://support.apple.com/HT204084