[VoiceOps] Avaya IP Office sending Caller ID

Hi Gents: Say if you have 2 extensions with following inbound routing to those on an Avaya IP Office: DID 3035551000 routes to ext 1000 DID 3035552000 routes to ext 2000 For outbound calls how can I make sure the DID 3035552000 shows up as the CallerID number. It only seems to Display 3035551000. The Avaya is sending the INVITE out to the SIP provider with 3035551000 in the FROM header even though SIP user Ext 2000 is making the call. Any ideas?