Hello I really will appreciate the support of the 3CX users out there. I think there is a simple answer to my question which I don't get: First, here is the LOG in question: INVITE sip:email@example.com:5060;rinstance=0ab91c6fadb6acd1 SIP/2.0 Via: SIP/2.0/UDP 220.127.116.11:5060;branch=z9hG4bK5ti6ceig4uvpdeaojahhi3kbk6 Max-Forwards: 69 Contact: <sip:18.104.22.168:5060;transport=udp;wlsscid=1ae4691c270666;appsessionid=app-1etnv1symb1bm> To: <sip:firstname.lastname@example.org:5060;rinstance=0ab91c6fadb6acd1;transport=udp;useradd=22.214.171.124;userport=5060> From: "Unknown"<sip:email@example.com>;tag=SDe3c7001-1312b5db Call-ID: SDe3c7001-6bd6cb1342e08d2324953ab7899de1de-gurpkk2 CSeq: 1 INVITE Allow: INVITE Supported: replaces Content-Length: 0 X-DID: 9415387840 X-UUID: 295cfc330b7a491caf1f76431376a387 The main SIP account at SIP provider (Inphonex) is say 7557777. I am able to buy a number of direct numbers to link to this one sip account (7557777). One of the DID numbers is mentioned in the log above US# "9415387840". How can I guide 3CX to look for the DID number in the X-DID field? I am not familiar with SIP coding/fields at all. As you can see the DID number is not shown in other fields apart from the X-DID at the end? I am familiar with the DID settings, the problem I think is with the SIP field configuration selection "SIP Field containing DID numbers:" in (VOIP Providers > Inphonex > DID). Which one of the drop-down items will have the value of the "X-DID" field? (Request Line URI: User Part, Contact: User Part, To: User Part, From: User Part? etc.). I have tried all - with no luck. Do I need to change/add the SIP field values in 'Inbound Parameters' (VOIP Providers > Inphonex > Inbound Parameters). to look for the "X-DID" which will then trace through to the "SIP Field comtaining DID numbers" selections? Thanks!