Any type of purchase, whether deliberate or accidental, is handled by the payment platform that you used for the transaction. Requests must go through the platform's resolution center. We strongly recommend that you set up Parental Controls on your device to avoid this in the future.

Google Play Support: https://support.google.com/googleplay/?hl=en#topic=3364260
Apple Support: https://support.apple.com/contact
Amazon Support: https://www.amazon.com/gp/help/customer/display.html?nodeId=201357410
PayPal Support:  https://www.paypal.com/us/smarthelp/home