Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello
If you switched from Basic to Family, the amount of time added to your Family plan is calculated at a 18% conversion rate.
If you go to your account, https://account.live.com > Subscriptions, if you look at the expiration or renewal date for the family plan, does it show partial year, or a full year? If it shows partial year, then the basic plan has been converted, so there's nothing to cancel so to speak.
If you see a full year of Family plan, then I need to know—was the basic plan originally purchased via Microsoft directly, or via third party?