The "People" page on web is where you can manage the list of people on your account. Here you can add people and manage permission levels. You can also remove people from your account by completing the following steps:
1. Login on www.fieldwire.com and head to the People tab.
2. Find the user you'd like to remove and select the dropdown (which specifies their permission level).
3. Select "Remove".
Once removed, the user will no longer count towards your total user count (and billing).