We have one advertised phone number (vanity number) that customers call into. This number is permanently call forwarded to a group of 3 lines (on a different C.O. switch) coming into our PBX. We've discovered that the advertised number does not handle simultaneous call forwarding and the local provider wants to now charge us for 3 lines each with a call forwarding feature for the same number (advertised vanity number). Is there a better/cheaper way to accomplish the same thing?