If a new worker has arrived and a previous user is no longer active, we suggest adding a new user login and disabling the old one, rather than changing the existing login.
This is primarily so that when reviewing past work done, you can easily tell which user completed the task and track the activities of both individuals separately.
Also, once disabled, users do not factor into your pricing going forward aside from any uncharged period beforehand.
Instructions for adding and disabling a staff member can be found here:
Adding and Managing Users