I have a Seimens HICOM 300 connected to a Cisco 3800 Router via 4 PRI Interfaces. The Cisco Router is connected to my carriers SIP Network. If I try to forward a call from one of my digital phones through the SIP Network, the call does not go through since the calling parties Caller ID is forwarded to the SIP Network, and the SIP Network will not accept a DID that is not defined within there switch. My PBX does not allow me to change the forward caller id to a different number. Does anyone have recommendations on how to change the Caller ID from a Call Forward on a Cisco 3800?