Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
If you are unable to contact that person to ask them to cancel the subscription and you are unable to access their account to cancel the subscription yourself, it may or may not be possible to cancel the subscription since it is not linked to your own Microsoft account.
The best first option is to contact your bank to cancel the direct debit for the subscription.
If that is not possible, this forum is just a user to user forum, no-one here has any account access, you will need to contact Microsoft Support directly and explain the situation to them, they may be able to resolve this for you, try using this method to contact their support.
Go to this link: https://support.microsoft.com/contactus
Select Microsoft 365
Click 'Get Home Support'.
In the box provided, type billing.
Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.
Navigate to Microsoft 365 and Office - Manage my Subscription.
Select the 'Chat with support agent in web browser' option