I'm with Rogers in Canada. AT&T is Roger's official partner in the USA. I was on the phone all afternoon with both my carrier's text support and Apple
I baffled my carrier. After I did a full restore and created my iPhone as a "New device", it wouldn't allow me to toggle wifi calling. It said to contact my carrier. When I contacted my carrier, the rep rebuilt my entire profile and I still don't have wifi calling. I then restored my iPhone from a previous backup, I can now toggle wifi calling but it doesn't work. Wifi calling for whatever reason isn't connecting with my carrier. I do not have wifi calling in Airplane mode either when in the past I did.
Apple is replacing my device and I have an appointment next week at the Apple Store. I doubt this is a hardware issue, but whatever. I will take advantage of a new device even though mine is a about 6 weeks young.