What I've done:
Changed the phone number so it can be text and numerical. When you edit a ticket as a manager (or staff), you see a equipment id number: Example: 02-17-118A . When a manager or staff views the Ticket (or the end user in their view as well) .. they see 021-7118. How do I change the view for both the staff/manager, and the client view?
There are two files used one on the client side, one on the staff side. If memory serves me correctly they are:
/include/client/viewticket.inc.php
and
/include/staff/viewticket.inc.php
Good luck.