Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
The process to switch Microsoft 365 subscriptions is explained on the link below.
Basically in your case you are upgrading to a version with more features, what happens is you will be charged for a full new subscription and the remaining time on the original subscription subscription is converted to the new subscription on a pro-rata percentage basis (60%), check the expiry date on your new subscription to ensure that has happened.