NOMOROBO works just fine for me on Xfinity Voice Unlimited. Just go to http://www.nomorobo.com/signup and follow the steps. You'll need to go into your Xfinity Voice Prefrences and edit your Advanced Call Forwarding to include the NOMOROBO phone number. When someone calls your number it will ring all the numbers in your list including NOMOROBO. If NOMOROBO detects the number as a robo call they will pickup the call on the first ring causing all the other phones in the list to stop ringing.