atcomsystems.ca/forum Forums TDM Business Telephone Systems Avaya - Lucent Telephones & Systems Change Outbound Caller ID - IPO 406 v 4.2

Sets it to National (if remembering correctly - you could consider looking at documentation to be sure). In my world, it makes it work more reliably for many cell phone carriers. That's all I use and it works fine at every location.
Mike