Within Teamwork.com, you can downgrade an existing standard user to a collaborator.
When you downgrade an existing user to a collaborator, they will not count towards the cost of your subscription but they will have reduced permissions compared to standard users.
Click the More option in the main navigation menu and select People from the pop-out menu.
In the People tab, click the name of the relevant user to view their profile.
In the top right of their profile, click the options button (three dots) and select Downgrade to a Collaborator from the dropdown menu.
You will be asked to confirm if you want to downgrade the user. Click OK to save the changes.
Alternatively, you can click the three dots to the right of the user in the list of people and select Edit Profile.
In the user details modal, you can change the Type field to Collaborator. Click Update to apply the change.
For more information, see: Downgrading a User to a Contact