When you remove a client, they will have read-only access to their account. They'll have to subscribe so it will become active again.
Here's how:
Go to the Gear icon ⚙.
Choose Subscriptions & Billing.
Select any clients you want to remove.
From the Batch Actions ▼dropdown, select Transfer billing to the client.
Click Remove.
I'd suggest visiting this website: Manage Clients with Wholesale and Direct Billing. In this link you'll learn more about adding, removing, and transferring clients in and out of wholesale Billing.