Will the presence of a working battery ensure I will have phone service?

In the case of a complete power loss, network outage, broadband Internet outages or congestion, disconnection of service, or other conditions beyond the reasonable control of WAVE, you may be unable to access 911 or your access to 911 may be delayed or impaired. 

If you utilize cordless phones in your home, WAVE advises you to keep a corded (landline) phone on hand. Corded phones, unlike cordless phones, don't need a separate power source to operate and can function with a battery backup in your WAVE Voice modem during a power outage.