Play "Number Not In Service" for dormant DIDs

there is a Freepbx way to do that Image may be NSFW.
Clik here to view. (this one based on FreePBX 12.0.76.2 )

Admin->System Recordings->Built-In Recordings (the last link is on right hand side upper corner)

select system recording - click on the drop-down, start typing ss-noservice, should autocomplete/hint - then click 'go'

then on next screen, give it a name (no spaces allowed - it will prompt you to change if it doesn't like it), then Save;

then in Connectivity->Inbound Routes, set the DID destination to Announcements, and there you will have the recording you just named, available on the list;

Set other options as neccesary.

Set the destination after announcement, to terminate/hang up.