Is my Android asian phone blacklisted?

syaoran wrote:

Getting VoLTE and VoNR to work on them that is compatible with T-Mobile can be why.  Sometimes an update to the device can change the carrier profile, roving compatibility for VoLTE and VoNR that works with T-Mobile USA.  These devices might have the correct bands but VoLTE and or VoNR also needs to be compatible to make and receive calls.  

 I wish it was easier to find information about VoLTE & VoNR. All I know about them is you got it or you don’t and if you buy a phone not designed for the US market, it maybe won’t work.