Yes, if you just mean you want to change the text so instead of Phone 2 it says something else like Mobile Phone you can do that.
it is done by creating a text file called CustomLabels.properties with the 'replacement' labels you want to be reflected in the product, and then putting that file in the \WebHelpDesk\conf\labels folder and restarting Web Help Desk using the 'stop web help desk' and (later) 'start web help desk' icons from the Start Menu. (<-- i'm assuming Windows install here!)
The particular (and possibly the only) line that you would want in that text file is:
lbl.phone2 = WhateverYouWantToCallIt
lbl.phone2 = Mobile Phone
^^That's the short version; there is a description of the how here: