Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello,
Was this a purchase made via Apple Store on your MacOS? If so, you need to request it from Apple, not Microsoft, because the payment processed via Apple.
Microsoft explains it here:
Apple's refund request instruction is here: https://support.apple.com/118223
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If you decide to keep the one subscribed via Apple and rather cancel the one subscribed via Microsoft, Please go to https://account.live.com
Sign into your Microsoft account. Then go to Subscriptions. Click on Manage for the subscription plan you want to cancel.
Then ask for 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.