The is a two-part problem most likely stemming from the same issue. Supposedly it was fixed in CR276601026, but that proved to be false.
First, when I log into my xfinity account on my computer, I can manage all features normall except Voice. I can click on Email in the upper right to view email. I can click on TV to control my DVR. I can click on My Account to pay my bill. However, when I click on Voice, it seems to think I don't have Voice service (which I do). I takes me to http://www.comcast.com/Corporate/Learn/DigitalVoice/digitalvoice.html.
Second, when I use my iPhone 4 with the most up-to-date app, I can control my DVR and check my email. When I click on Voice, it says "We cannot find your voice mail. Please check back later. If you still cannot find your voice mail, then please contact Comcast through the link in the Help section."
Also of note is that when I click on Help, there is a box on the right side of the page that say "Connection Status". Only Internet and TV are listed.