Cal here from Shopify, thanks for reaching out to us. I'm sorry to hear that you're looking to cancel your store, was there anything in particular that caused you issues?
Have you closed the store? If you have, then I can look to investigate a refund. If not, you can close your store by following these instructions:
1. Log in to the admin section of your store.
2. Click on Settings.
3. Next, click Plan and Permissions.
4. From there, Scroll down to the bottom of the page and click "Close my Store".
Let me know when the store is closed, and please share the MyShopify URL for the store with me here so I can investigate the account.