Lee, I thought you could specify the phone as voice only instead of Voice and Fax.
Under Phone System --> Phone Numbers, select the direct phone number and then change the number type to Voice Only.
Perhaps someone can clarify if this is the correct function
That was my first thought also, but there is no option under phones. All I have I have is remove line. If I view the properties of the phone number It does say, Number type: Voice with no options, but i am still getting faxes.