DanishbluntAnd, if you're willing to root your phone, you can force enabling VoLTE/VoWiFi even if it isn't officially supported:
Since this varies greatly from person to person I would like to create this topic in order to make the devs figure things out easier.
Fill out the following:
( type in calling app: #*#4636#*# for getting the information )
Video Calling Provisioned: Yes
What doesn't work:
VoLTE doesn't work, Wifi Calling works fine.
@Mattias_ASUS You can tell the devs to look for this topic to fix further VoLTE issues. Some cant use Wifi Calling, others have VoLTE enabled in settings but doesn't actually work on their phone.
Wifi Calling / VoLTE not working? Look here!
Since I'm impatient I decided it would be the best course of action to enable VoLTE myself.
For those who have root, you can basicially follow this guide:
P.S If you have trouble etc. refer to the thread on XDA. In my case VoLTE never worked only Wi-Fi calling, probably due to borked configuration file and since I didnt really feel like doing a reflash, i fixed it myself via qualcomms diag.
Keep in mind, if something goes south you can brick your device, so be warned.
enabling VoLTE yourself