If you subscribe to Comcast Voice, there maybe a feature you have and don't even know about - Call Filter.  Simply dial *60 from your home phone and activate the service, which is free.  Follow the voice prompts to add numbers to the list.  Do not dial "1", but must use a 10 digit number.  If you dial a "1" the system will not accept the number.  When you are done, all those numbers you entered will never bother you again