Each in-game purchase is processed by the app store you downloaded the game from. To request a refund, you need to contact your store's support service.

To speed up the refund process, we recommend providing full purchase information: order number, time of purchase, or a receipt.

Cancel a purchase on the App Store - https://reportaproblem.apple.com/?s=6
Cancel a purchase on Google Play - https://support.google.com/googleplay/contact/play_request_refund_apps
Cancel a purchase on the Amazon Appstore - https://www.amazon.com/gp/help/customer/contact-us