@Jmtelco you need to make sure your provider allows you to send what you want, plus it also needs to be in the correct format. Some providers require full E164 whereas others will accept anything. You also need to know where to place the outbound ID, again some look at different parts of the invite header, Contact, Remote Party ID, P-Asserted, From, etc.
If you create a dedicated Trunk URI for outbound calls needing to show the DDI number then select as they guys mention USE USER DATA in all fields. The fields are populated in the invite message like below: (notice the Display_Name, LocalURI and Contact Fields). If you want a group of users to send the same number you can either populate their SIP USER TAB with the same number or create a new SIP URI Trunk with this number and use USER Rights to route calls via this trunk, saves a lot of inputting.
It would be a lot simpler if Avaya allowed the sending of the E in short codes or E_Name as the SIP USER TAB is defaulted with the User Name.
58806522mS SIP Call Tx: 65 INVITE sip:0161901222@78.133.160.155 SIP/2.0 Via: SIP/2.0/UDP 88.88.250.250:42150;rport;branch=z9hG4bK3bee050e9877dced8d425fa7849551e7 From: "Display_Name" <sip:LocalURI@78.133.160.155>;tag=5f69288530af88ca To: <sip:0161901222@78.133.160.155> Call-ID: 6f0b4d3ec37b1e5484933928fafd8a3c@88.88.250.250 CSeq: 2011656963 INVITE Contact: "Display_Name" <sip:Contact@88.88.250.250:42150;transport=udp> Max-Forwards: 70 Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, INFO Content-Type: application/sdp Content-Length: 276 v=0 o=UserA 2032068258 264965973 IN IP4 88.88.250.250 s=Session SDP c=IN IP4 88.88.250.250 t=0 0 m=audio 49154 RTP/AVP 8 0 18 101 a=rtpmap:8 PCMA/8000 a=rtpmap:0 PCMU/8000 a=rtpmap:18 G729/8000 a=fmtp:18 annexb=no a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15