Clean flash steps for VoLTE
Shank03- Use newflasher or flashtool to flash stock ROM of your region. (Do this even if you are on stock ROM)
- Boot it and skip all the setup steps whatever you can.
- DO NOT SET ANY PASSWORD
- Make sure your VoLTE works on stock properly.
- Flash TWRP from below link and boot to TWRP.
https://androidfilehost.com/?fid=4349826312261733451
- Flash the ROM zip and reboot.. :)
- In above steps, you have dirty flashed the ROM, so if you get some bugs, you can factory reset from custom ROM (havoc).
NOTE: You can do the #volte_enabler(note in the group) step before or after flashing ROM..