I chatted with AT&T and here is an excerpt of the chat:
Jessica: Yes David, you can use WiFi calling and texting on the Razer 2 phone

Me: Thank you, there have been many reports of it not working, even on an AT&T branded phone.
Jessica: The device used to have some problems with it when was launched, however all of the carriers fix that issue directly with the manufacturer and now it works perfectly
Jessica: I understand your concern, but no worries, that won't happen
Me: Awesome! Thank you, have a great day.
I still don't know for sure but with this I may just order one to give it a try. If anyone has anything they can add, please do.