When setting up Users there should be a level of consistency with User profiles. Eg. SamA - [First Name, Last Name Initial] or SArmstrong [First Name Initial, Last Name]
When updating usernames, it will not send an updated login via email to the user.
You will have to email each user with their updated Username and their password will remain the same, alternatively you can change their username and then reset their password.
They will then receive a system generated email form Xplor with their updated user logins.
> Select User
> Change User Name
> Either email User or Reset their password to send updated login