Items bought through our games (In-app purchase) are generally non-refundable. In some special occasions there can be exceptions. The transaction process is controlled by Apple and Google.
Please contact Apple or Google support teams for refund issues.
iOS:
Visit Apple support and select the "contact iTunes store support", then "Purchases, billing and redemption" and select the option that fits you.
Google:
Visit Google support and perform a serach, or "Contact us" button on the page to reach a Google customer support represetative.