After 11 years of living in this house with basically no cell service, my iPhone is suddenly as useful at home as in town.
AT&T turned on wi fi calling. I can make and receive calls and texts over my wifi connection. The only flaw is that Siri doesn't seem to know it's there, so if I try to voice dial, Siri says I don't have a good enough cellular connection. However address, recent, dialing all work great.
Go to Settings/Phone and you'll see an enable button.
This is hugely great news for me. Now, I wonder if I'll be able to make calls from the ski lodge which has no service either? Probably.