[Freeswitch-users] How to set alternate presence_id when extension dials out?

Hello, I have a scenario in which one user is associated a unique registration for each of 4 total devices they use, and one extension (say 2000) is sort of a dummy extension that all it does is ring the devices in a certain order using its dial-string, from which I can set the presence_id to trigger, ie. 2000@domain. That's the easy part. Where I'm struggling is... how do I force those other 4 extensions to trigger 2000@domain as the presence_id when they call out either internally or over a gateway? (their extension number is random digits, insignificant in this case as no one will be monitoring BLF on those unique registrations). Thanks Mike