gchiu: Sadly not working. I get a message that call can not complete as dialled.
Dunno if this is relevant but when I created the route, it insisted I needed a dial pattern so I just made up a few like this
These aren't valid. You just need a simple route with X.
You'll then need to work on dialplans for the phones, the default ones are horrible and will restrict some calls along with a long timeout period after dialling the number unless you press #