If you have one with Apple, you need to check it in your Apple account, and if you want to cancel it and request refund, you need to do it with Apple.
Microsoft explains it here:
https://support.microsoft.com/account-billing/how-to-get-a-refund-on-a-microsoft-subscription-67dca30b-b323-44d5-acc2-e02f9902c472 
Apple's refund request instruction is here: https://support.apple.com/118223
On the Microsoft side, if you have a subscription, it should be listed in https://account.live.com > Subscriptions. You can click on Manage, and cancel it on the next page if this is the one you want to cancel instead.