If you use both Xfinity Voice and Xfinity Internet, use your Comcast ID and password to log into your Comcast account through the Email tab on the site's home page. From the Preferences tab, access the Call Manager and select Call Screening..urning It On. As a Comcast phone subscriber, you can activate anonymous call rejection from your telephone. Pick up your receiver, or press Talk on a cordless phone, and wait until you hear a dial tone.