I am trying to use 3CX as a go between, between my ITSP, and a traditional Samsung iDCS 100 PBX. The pbx supports sip, however it is not fully compliant, so I need to send everything through the 3CX and treat the traditional phone switch as an extension. This works perfectly in all respects other than inbound DID routing. The ITSP sends me the 11 digit DID info, and I can route it to the extension that the phone switch has registered at, however when the 3CX sends the call along to the Samsung PBX it strips all of the DID info out of the to and the contact fields of the sip invite request, and therefore the Samsung always gets the 3 digit extension number and does not know how to route the call based on DID. Is there a way to set it to keep the extension in the to field of the sip invite request, however show the 11 digit DID in the sip contact info as the sip RFC suggests doing?