As with most downloadable software products, items bought through our games (in-app purchases) are generally non-refundable. In some special occasions there can be exceptions, however. The transaction process is controlled by Apple (for iOS devices) or Google (for Android devices), and both companies have support teams who handle refund requests.
For Apple (iOS) devices:
Visit Apple support and select the "Contact iTunes store support" link, then "Purchases, billing and redemption" and choose the option that fits you best.
For Google (Android) devices:
Visit Google support and perform a search, or use the ‘Contact us’ button on the page (English language site only) to reach a Google customer support representative by email or by phone.