To remove an employee who is no longer working for the company, do the following:
Go to 'My Company'
Go to 'Employees'
Find the user you want to remove
Tap the three dots on the end of the user
Select remove user 'Remove member from company'
When you click on 'Remove member from company', you will receive a notification, to check that you actually want to remove this user.
If you press 'OK', the user will be removed.
Below is also shown how visually:
Find the right user:
When you press 'Remove member from company', a warning will appear:
This is not the same as removing a user from a project. There, all projects that have this user's stored history will be named with 'the person's name' while the user will not be found under the users in the company.
Hope this was helpful!