Suggest recreating one of the area codes as an NPA (if you are using 10 digit dial). Since this is a branch office, in normal condition, are all phones registered to the main office (IP)? If so, you will need to verify your ip zone dialing at the branch office. I believe in order for zone dialing to work properly you will need the proper digit manipulation in order to strip the zone number once the outbound call hits the main in order to dial out on your first choice; PRI. On my first comment, SPNs in LD 90 can be very limiting especially when tandem-ing across networks.
