Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
The steps to cancel the subscription are provided on this link and while managing the subscription, be sure to disable recurring billing on the subscription..
You should then be entitled to a pro-rata refund, you can check your eligibility to a refund using the steps on this link.
If you are unable to resolve the problem or cancel the subscription, this forum is just a user to user forum, to protect users no-one here has any account access, 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