[Old How-To, if the current one doesn't work for you, try this way]
1)To be safe, make a backup via TRWP of your EFS partition BEFORE you flash anything! If you're not rooted, do a nandroid backup via fastboot
2) Download and install:
https://jamal2367.com/VoLTE-VoWiFi/QUD.WIN.1.1 Installer-10037.3 Setup.zip
Just use the standard settings and click on OK, next, ...
3) Connect your phone to your laptop via USB
4) open dialer app and enter *#801#
Set Serial and Full-port switch to ON
5) Open "Software Download" in your QPST start menu folder, best to do by right click & "run as administrator"
Go to: MCFG_PDC (to the right), select your device, right click on "Oversea-Commercial_DS" and deactivate Sub0 and Sub1
Click on Oversea-Commercial_DS again and click on remove
6) Close the app and reopen it
Go again to MCFG_PDC, select your device, scroll down to Telefonica_UK_Commercial, right click and SetSelectedConfig for both Sub0 and Sub1
Click on Telefonica_UK_Commercial again, then to the right on Activate and on Start --> you will not see a confirmation screen, so don't be surprised
I received an error but it still worked.
Yes, select UK even if you are located in another region (see above for comfirmed locations + carriers)
9) Restart your phone
10) Voila, you now have working VoLTE + VoWiFi
Can anyone please provide a usable source? These sources are no longer working: and redirecting to homepage