Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
1
That subscription is most likely Microsoft 365 Premium.
Log into any Microsoft account you may have on this link.
https://account.microsoft.com/services/
Do you find the Microsoft 365 Premium subscription listed there?
If so, select that subscription and click Manage.
In there, you can cancel the subscription and also ensure you disable the recurring billing setting to ensure no further payments are taken for the subscription.
You should then be entitled to a pro-rata refund, you can check your entitlement to a refund using the steps provided on this link.
2
If you are unable to find an active subscription on any of your accounts, this forum is just a user to user forum, for account security 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