Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Please make sure you cancel from the account you don't need the subscription first.
Please go to https://account.live.com
Sign in to your Microsoft account. Then go to Services. Click on Manage for the subscription plan you want to cancel.
Then contact support to request a refund.
Go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Microsoft 365" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.
You can reference this detail step by step instruction with screenshots I posted in this thread: https://learn.microsoft.com/en-us/answers/c/2714817