In a new install with a clinic, they call forward their main number to an all night clinic. Both area codes are 843. If a call comes in from 843 area code all is well. If a call comes in from any other area code like 864 then the PBX puts that area code (864) in front of the 7 digit number to dial and of course the call does not go through????? There is a PRI in the system, but the PRI has been working for years in a 200ICP with zero issues.