As soon as a user is verified, he will gain access to the portal. It is possible to manage the access of a user to the portal.
This can be done at the organisation details page and under the actions button
Removing a user: Suspend
You can suspend users so they no longer occupy a seat.
Click on 'Actions' and 'Suspend'.
Replacing a user: Suspend and invite
A direct replacement of a user is not possible; you should first suspend the user and invite the new user.