Originally Posted by
libra89 T-Mobile is a little better than AT&T in this regard. It just so happens that Windows Phones are not really cared about when it comes to unlocked phones with carrier features. There are several unlocked Android phones that have HD Voice/VoLTE. Not sure if you know this already but the Pixel is just like how they treat iPhones, everything works without a hitch or any work required.
I get everything with my sim-free iPhone without any work or problems. Even though it isn't T-Mo's phone, it recognizes it as a phone.
I can't speak about the Pixel but I do know that if a phone is not "certified" by T-Mobile, it won't get VoLTE. It'll work as far as data and voice, but HD calling and sometimes Visual Voicemail and/or WiFi calling won't work. Being the chronic switcher that I am, believe me, it's infuriating. As for iPhones, my monster-in-law's AT&T unlocked Iphone 6 and her warlock husband's 5C don't get the goodies either. BTW, my wife is very aware of my monikers for her folks. In fact, she calls her own mother "Godzilla" and we have a Godzilla roar as a custom ringtone for her. Happy wife, happy life.