OK, maybe I am not understanding, let me try to touch on everything... You verified:
- The outgoing extension is the same as phones that work
- The day and night COS are the same as ones that work or blank
- House Phone is set to NO
- In CO Trunk Groups Outgoing Access, Answer Access, and Emergency Access the extensions are listed, or are part of the extension list (Most systems use 'PP051 Auto: All Stations' by default, but check that it is there and that those extensions are in that list!)
If these four things are good, your extension should be able to dial out...
If these don't work, are you using ARS (outbound extension set to 92000)?