Glitchy and Temperamental
Real problem with iPhone Speaker use..
NOTE: This happens across iOs updates, over different iPhone models, over the span of two years, and over years of reboots of the AT&T unit.
Honestly, after a power failure in the house the AT&T unit loses power and does not auto-start. I can use our registered iPhones ( in most areas) just fine without the unit on. If I walk by the unit and notice it is powered down, I will turn it back on. Our phones might auto-pickup a good signal with our wi-fi and use that to successfully manage calls without the AT&T unit.
We need the unit because our residence has stucco on the outside with wire mesh underneath. This creates a faraday cage around our whole house ( except for the roof, doors and windows).