Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
1
Log into any Microsoft account you may have on this link, do you find the Microsoft 365 subscription listed there?
If so, click Manage on the subscription and from there you can cancel the subscription to get a pro-rata refund, and also disable the recurring billing on the subscription to ensure no further payments are taken from your account.
https://account.microsoft.com/services/
2
If you are unable to find the subscription, using any Microsoft account you may have, try using the steps they provide on this link to find out what that payment was for.
Then use the steps they provide on this link to cancel whatever that payment was for and get a refund.