As all payments in Android are handled by Google Play, you should send your refund request directly to Google Support:
- Open Google Play account page from PC.
- Click on the three vertical points icon in the ACTION column and choose "Report a problem" for the app you want to be refunded.
- In the drop-down menu select the "I'd like to request a refund" option.
- Fill out the reason why you want a refund and click on the "Send Report" button.
Unfortunately, we can not issue refunds for our apps and in-app purchases, please contact Google Support about this issue.