You can request a refund through the Google Play Store if you contact them within 48 hours.  

If your purchase was made over 48 hours ago, please contact our support team through the contact form below and include in your message the transaction ID (which looks like this: GPA.XXXX-XXXX-XXXX-XXXXX). As long as you still have the currency in your account, the package can be deducted and the refund can be issued.  

If you have spent the currency or traded items already, we will be unable to process your refund request.