This app was mentioned in 2 comments, with an average of 2.50 upvotes
Telephone lines have all kinds of crazy regulations regarding privacy of call records and billing information. The Home phone number is one of the things that always has to be authenticated when changing pins. Its also a way for comcast to Identify who you are. Sometimes we had to call customers back on there home line to authenticate that it was really them.
The xfinity connect might be useful for you. It allows you to make calls and texts using your xfinity voice number from your cell phone.
https://play.google.com/store/apps/details?id=net.comcast.ottclient&hl=en
https://itunes.apple.com/us/app/xfinity-connect/id320788270?mt=8
Now, can you help me with your reddit password?
Comcast has an app called Xfinity Connect. It allows you to make/receive calls on your cellphone/tablet. Until you can get the issue resolved, you can use the Connect app. It's available for Android and iOS.
https://play.google.com/store/apps/details?id=net.comcast.ottclient