[MENTION=136639]zafarabbasrizvi[/MENTION]
So I only have a temporary Etisalat SIM right now, and after adding it, VoLTE toggle showed up in settings, but it was greyed out. I bought the SIM on 16th Sept, and this morning suddenly VoLTE icon showed up in status bar, the icon is no longer greyed out and IMS status says 'Registered' in settings.
So VoLTE is working for me, and I didn't do anything to enable it. I checked settings and under APN list, a new profile called IMS was automatically added.
Add the following to your phone and reboot it:
Name: IMS
APN: ims
MCC: 410
MNC: 01
APN type: ims
APN protocol: IPv4
APN roaming protocol: IPv4
Mobile virtual network operator type: None
Add this, but don't enable it. Keep the normal Jazz APN selected.
Reboot your phone and see if the VoLTE toggle becomes available for you to enable/disable.