Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
If you cancelled the subscription as soon as possible after your were charged for the subscription, then you should receive a full refund, it may take 5 - 10 business days to receive the refund.
If you do not receive the refund, this forum is just a user to user forum, you will need to contact Microsoft Support directly, try using this method to contact their support.
Go to this link: https://support.microsoft.com/contactus
Select Microsoft 365
Click 'Get Home Support'.
In the box provided, type billing.
Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.
Navigate to Microsoft 365 and Office - Manage my Subscription.
Select the 'Chat with support agent in web browser' option