If you have ATT home phone service you will either have POTS (Plain Old Telephone Service) aka 'land line' or VOIP (Voice Over Internet Protocol).
Your Uverse bill is broken down into the individual services you may have: TV, Internet, Uvoice so yes, your UV bill will show either Voice200 or Voice Unlimited (there is also a Voice International). See all options HERE
Since the RG (modem) is the source of all services (see above), if there is a power outage, your phone service will be affected by a power outage.
I've had UVoice for 6 years so I can only go by my experience. I was given a BBU (Battery Back Up) which provides 4 hours of power. It is my understanding that that policy has changed.
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