aeverson

This is a big stretch but try this:

on the 403 try the following short code:

Shortcode = [9]1N;
telephone number = 81N
line group ID = VoiP Line ID


On the 406 enter the following short code
Shortcode = [8]1N;
telephone number = 1Nsi777 (777 can be any number you want it to be to identify your 403)
line group ID = PRI Line group ID


I bet if you look at your short codes you will see a telephone number with "si224" in it. Thats how you tell the local phone company what number to display on the remote ends caller ID. Thats the only way I can see that the phone company is able to capture the extension number from the IP office.