Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
The process to switch from a Microsoft 365 Basic subscription to the Personal subscription is provided on this link in the 'Switch to a version with more features' section.
Basically, when you upgrade from the Basic version to the Microsoft 365 Personal version, any remaining time on the Basic subscription is added to extend the Personal subscription on a pro-rata percentage (24%) basis.
Check the expiry date on your new Personal subscription on your Microsoft account online (https://account.microsoft.com/services/) to ensure that the Personal yearly subscription date has been extended.