Refunds only are possible in some specific cases where a problem came up during the purchase. 
If you made a purchase on an Apple (iOS) device:
For purchases made on an iOS device, we have no authorization to handle refunds on your behalf. Please contact Apple support and explain your case.
If you made a purchase on a Google (Android) device:
We would need you to contact us and send us a screenshot of the specific receipt. Please be sure the transaction ID appears there. It looks like this GPA.1234-1234-1234-12345 You can find all your purchases made on Google Play in your Google Payments account