I'm looking at a migration and trying to see if there is a way to route to phones on another system when extension dialing. For example, I have extension 1000-1999 and will migrate some of those extensions in waves. Is there a way I can tell Fusion that if the 4-digit extension doesn't exist on the system to send to a gateway? I tried creating an outbound route with the 4-digits drop down and it doesn't seem to work.