Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
1
Log into your Microsoft account on this link.
https://account.microsoft.com/services/
Click the Manage button on the Microsoft 365 subscription
In there, you can cancel the subscription and also disable the recurring billing on the subscription.
2
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 pay for the subscription through the Apple App Store, you will need to contact Apple support to arrange the refund.