Not possible to use Chat for Xfinity Internet Support as form requires Phone Number and no such field exists.
Hi, DarrenMossman - Are you signed in to your account? What topic did you choose? I just tried to chat from my personal account and I didn't get an error message. Could you please go to My Account -> Contact Information and confirm that your phone number is correct (please make sure it doesn't say (000)-000-0000 or (123)-456-7890)?