The customer has an AT&T Definity G3 switch/PBX and has configured an incoming ISDN trunk. When calling from a Cisco Call Manager v.12.x we receive a busy. The path is Cisco CM - Media Gateway using MGCP, PRI,B8ZS,ESF, Calling from the PBX into CM no problems good two-way voice all. Again the problem is calling into CM. Can someone Please Help I need detailed steps on the configuration from the PBX side? Any HELP will be Greatly appreciated.