How do I get a refund on Google Play?

 Google cannot cancel orders on behalf of the seller. To contact the seller with a cancellation request or details about an order cancellation:

  • Sign in to your account at https://wallet.google.com/manage 
  • Click View Order
  • At the top of the receipt, click Contact [Seller's Name]
  • Select I'd like to request a refund or return an item from the Subject drop-down menu
  • Enter your message in the Message text box
  • Click Send email after you've provided the necessary details.

The seller may or may not be able to accommodate your cancellation request depending on the seller's policies. Cancelled orders are automatically refunded and cannot be reinstated.

http://support.google.com/googleplay/bin/answer.py?hl=en&answer=113515&topic=1046718&ctx=topic