Since your membership was purchased through Google Play and not ChessKid.com, you will need to start a refund request directly with Google Play.
To see your Google Play refund options, please follow these steps:
Select Order History
Find the order you want to return
Select Request a refund or Report a problem and choose the option that describes your situation
Complete the form and note that you'd like a refund
You'll receive a message that says "Thank you for sharing your concerns." Shortly after, you'll get an email with your refund decision, usually within 15 minutes, but it can take up to 4 business days.