Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Before cancelling the subscription, if you store your files on OneDrive online, you would loose access to the 1TB of OneDrive storage, you need to be sure you have a safe copy of your files before cancelling the subscription.
Then, log into your Microsoft account on this link (https://account.microsoft.com/services/), click the Manage button beside the subscription you want to cancel, and from there, you can cancel the subscription and also ensure you disable the recurring billing on the subscription.
When you cancel a Microsoft 365 subscription, you may be entitled to a pro-rata refund for the remaining time on the subscription, you can check your eligibility to a refund using the steps on this link.