I was looking at that section - NANPA is enabled
At first I left the "home" area code section blank.
Then I added my (519) area code as home, and made note that the area code needed to be dialed - For some reason I am not seeing this on the system. Faily sure I tried a reboot too.

I did notice that one of the phones was fine doing this, while the others seem to not work. Perhaps a residual programming thing like you are talking about.

I didnt think there were any settings on the phones themselves in relation to this aspect.

Another small question - When you are talking on the phone and an incoming call comes in, your phone will still ring out loud. Most people find this distracting - is there somewhere to change this? If someone is on the phone, do not let their extension ring?

Thanks
Chad