Incoming call routing is controlled by rules on each trunk's InboundCallRoute. Rules are evaluated left to right and the first matching rule wins.
To have a few callers go to the Auto Attendant and the rest go to the PHONE Port:
Voice Services -> SPx Service -> X_InboundCallRoute : {(12345550001|12345550002|12345550003):aa},{ph}
would send callers with CallerID's of 12345550001, 12345550002, and 12345550003 to the Auto Attendant and the rest to the PHONE Port.
To have a few callers go to the PHONE Port and the rest go to the Auto Attendant:
Voice Services -> SPx Service -> X_InboundCallRoute : {(12345550001|12345550002|12345550003):ph},{aa}
would send callers with CallerID's of 12345550001, 12345550002, and 12345550003 to the PHONE Port and the rest to the Auto Attendant.