It should work without WiFi if there is phone signal.
Almeuit knows more about the bands than I do.
As far as your router and WiFi range, sometimes your company will drop the range. I was suddenly not getting good coverage on one end of the house and called and they said it was too low and did something over the phone.
With my mom, I got her a Smart TV one Christmas and her router was in the office downstairs and there was no WiFi upstairs in the back where her room is. I called AT&T to see if they would bring her a router with better coverage. They just brought another router, no monthly charge and installed it in her room, behind a dresser. Many things can interfere with WiFi signal. You can also buy range extenders for WiFi at Staples. Walmart has them, but places like Best Buy, Staples, Office, Depot, have a better selection.
If you turn it off WiFi, how many bars do you have ever for signal?
I also don't know how well WiFi calling works, AT&T doesn't have it. I don't have good signal on my house, but I do have a microcell from AT&T in my house. The signal around me is good, down the street, just not great in my driveway or house. Others call it different things. It hooks up to my Internet and gives me 3G calling only and covers texting. I don't use it for getting online at home, but can. Some of the newer ones have 4G calling and data.
05-21-2015 07:01 PM