Using EC500 or Off-PBX stations will allow you to block inbound calls from specific telephone numbers at the PBX level. You need inbound caller ID in order to do this.
Step 1. Create a unique COR with the following settings: Calling Party Restriction = ORGINATION Called Party Restriction = INWARD
EC500/XMOBILE Method 2a. Create a new XMOBILE station. Put the offending phone number (the one that you wish to block) in the "Cell Phone Number" field. Set the "Mapping Mode" to ORGINATION, and give the new station the restricted COR that you created in step 1.
Off-PBX Station Method 2a. Create a new x-port station, and give the new station the restricted COR that you created in step 1.
2b. Create an off-pbx-telephone station-mapping for the next extension just created. Application = CSP, Trunk Selection = ars, and the offending phone number in the "Phone Number" field. On page 2, set the Mapping Mode to "orgination"; Calls Allowed to "none"; and Bridged Calls to "none".
All calls from this specific number coming into your PBX will now receive a wave-off tone and the incoming call will not be completed.