Cal here from Shopify, thanks for reaching out to us. I'd be happy to assist with this. If I'm understanding your request correctly, you had a Shopify store, and you were billed for a monthly subscription, but you would like a refund? Could you share the existing ticket number that you have with our support team?
If the store is not canceled I can't investigate a refund. The only way to cancel a Shopify subscription would be to close the account completely. We wouldn't be able to close the account in full for you here, however, you should be able to close the account by following the steps below:
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 you have canceled the store, and share your MyShopify URL for the store in question with me here. I'll then email the account owner with further information.