I have finally reach the limit with unsolicited marketing calls (in spite of being registered with the TPS). So today I have implemented a couple of changes to the Asterisk phone system here.
1. All inbound calls with the number withheld will be presented with the number disconnected tones, then told that the call may be recorded (it will be!) before any phones ring.
2. If the call is from a telemarketer, I will transfer the call to sip:firstname.lastname@example.org:5060
3. If they are already on my blacklist, they will automatically get transferred to sip:email@example.com:5060