To request a refund please first visit Google's cancellation policies at the following link https://support.google.com/googleplay/answer/2479637
If you don’t find your purchase when you try to request a refund through the link above, you can request a refund from the Google Play website:
Go to play.google.com.
At the top right, click your Profile picture.
Click Payments & subscriptions
Budget & order history.
For the order you want to return, click Report a problem.
Select the option that describes your situation.
Complete the form and note that you'd like a refund.
Click Submit.