Ash here from the Shopify team. Welcome to the Shopify Community.
I understand you've cancelled your Shopify account, but were still charged for the subscription. We generally don't provide refunds as per our Terms of Service, but our team can absolutely take a closer look into your specific situation.
We'll need to authenticate you on the account in question in order to check out the back-end, and authentication will need to be preformed via chat or email. Please head over to our Help Center and proceed through the prompts on the page. You'll then be presented with the current available options to contact our support team. Please open a support ticket from that page, and our team will then be able to help take a look into the possibility of a refund.