How to move user from a CSP Exchange Online licence to a Microsoft direct licence in the same tenant

I have an existing Microsoft 365 tenant with a single Exchange Online (Plan 1) licence that was purchased through Bluehost (Endurance International Holding B.V. CSP). Microsoft notified me that Endurance is no longer authorised as a Direct Bill CSP, so I decided to purchase a new Exchange Online (Plan 1) subscription directly from Microsoft

My current situation is:

• Exchange Online (Plan 1) purchased through Bluehost/Endurance
• Exchange Online (Plan 1) purchased directly from Microsoft
• Both subscriptions are now active

The problem is that Microsoft 365 appears to pool the licences together. Under Users → Active users → Licences and apps I only see Exchange Online (Plan 1) and there is no way to choose which subscription the user is assigned to.

The licensing page simply shows:

Licences assigned from all subscriptions: 1 / 2

The two subscriptions are only distinguishable by their billing profiles (one is the Bluehost/Endurance CSP subscription and the other is my new Microsoft direct subscription).

I want to make sure my mailbox is consuming the Microsoft direct licence.

• How can I determine which subscription my user is currently licensed from?
• If the user is still consuming the CSP licence, what is the supported way to move them onto the Microsoft direct subscription?
• Is the licence automatically reassigned if the CSP subscription is cancelled, or is there a manual process that should be followed?

I want to keep the existing tenant, mailbox, domain and email data and only change the billing source for the licence.

Any guidance from anyone who has completed this transition would be greatly appreciated.