Display Name can only be edited individually.
The confirmation dialog will only appear if you are selecting the recipient
from the Contacts Folder. There are many other ways to select recipients.
The standard behavior for the Outlook Address book is to display all
electronic addresses (both fax and e-mail). That behavior cannot be changed.
The only way to prevent the display of fax numbers is to store them in a
different field or to disguise them (e.g., precede them with an alpha
character) so that Outlook won't recognize them as phone numbers.
There are also a number of utilities available that can do this for you
automatically. Some are listed here:
http://www.slipstick.com/contacts/nofax.htm