Currently, there is no direct option in the Partner Center to upgrade from one subscription of Google Workspace to another. However, if there is a request to upgrade the product, this can be done by our technical team.
Things to note;
Upgrading from one subscription type to another cancels the product immediately. This process will not wipe out any information from the email inbox, nor from the drive storage, and Google Workspace users should see no disruption to their workflow.
This upgrade will incur a new charge for the new subscription.