On here you can change the name of a user, their extension number, their caller ID etc.
Nickname: To change the name of a user, simply delete the name under User Nickname and type in what you want the new label to be. The name should update on the handset straight away, however if it doesn’t you may need to give your phone a reset.
Extension: Similarly to the Nickname, you can just delete this and re-enter the extension that you need. It is recommended to leave this as it is, unless you have a specific reason to do so. If you do need to edit the extension number, we would recommend keeping it to a numbering scheme beginning with 2 (e.g. 20X, 200X).
Caller ID:
The number set in Caller ID is the default caller ID for all outbound calls made by an extension. You can set it as any numbers that you have on your system.