After seeing the above while connected to my iMac / iTunes, I unplugged my iPhone and then OK'd the carrier settings update. My phone went from AT&T 18.0 to AT&T 18.1, but I have yet to update to iOS 8.1.2.
I can go into Settings > Cellular > Enable LTE and I have the "Voice & Data" option. Unfortunately, I don't know if this just became available after updating to AT&T 18.1 or if it was already there before. I'm assuming this means I can now enjoy VoLTE (HD Voice)—on those rare instances when I call someone who
- has a likewise-capable handset
- has a postpaid plan
- has enabled the feature
- happens to be on AT&T
Is this really the only way I can tell I'm on an HD Voice call?
I would think that if I look at the status bar and see while the call is in progress, that would mean I'm on an HD Voice call.