Blocking incoming calls on single extension

Assuming these calls are coming in on a particular incoming call route / direct indial, this is what I do on my system:

1) Duplicate the users' existing incoming call route, but in the incoming CLI field add 'anonymous' like so:


2) Add a new short code with 'Barred'. The code should be something that suits your internal diel plan:


3) Configure that new incoming call route to send calls to the new barred extension (in my case, 2289):


Once you've done that any anonymous calls to that inbound number will get a busy signal assuming your trunks support it.

You could also send calls to any other supported destination like a Voicemail Pro module. I have one such route on my home system that allows calls with a caller ID to ring through but any anonymous calls go straight to the auto attendant (on Voicemail Pro).