There is a way to block harassing phone calls through Comcast Digital Voice. You must know the phone numbers that you want to block ahead of time.Once you have determined the numbers to be blocked, Comcast will automatically relay a message saying you are not presently accepting calls for up to 12 numbers total.ou must know the phone numbers that you want to block ahead of time. Once you have determined the numbers to be blocked, Comcast will automatically relay a message saying you are not presently accepting calls for up to 12 numbers total.