Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
On the link below are the steps provided to switch to a version of Microsoft 365 to another version with more features, basically that is a new subscription, then the remaining time on the original subscription is converted to the new subscription on a pro-rata basis, in this case that is 92%, if you check your subscription expiry date on your account on this link (https://account.microsoft.com/services/), you should have nearly 2 years left on the Microsoft 365 Family subscription
Because the 2 subscriptions will now have merged, if you cancel the subscription, that would cancel both subscriptions, the best option to resolve this may be to contact Microsoft Support directly, 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