Microsoft on-premises server product that runs Office Online.
Typically, you have to turn off recurring billing, if it is enabled, and then you should be able to cancel in your account at https://account.microsoft.com/services .
For more, see https://support.microsoft.com/en-us/office/cancel-a-microsoft-365-subscription-46e2634c-c64b-4c65-94b9-2cc9c960e91b .