FLYME is entering in to 6 with NEW HOPES but in one place failed that is HD voice symbol
if you switched ON light should ON this is actually normal phenomena.
But

iam seeing 5 to 6 till now we are not perfectly getting
IF VOLTE ON simply HD voice Symbol must appear without any interruption.
BUT why it is not accessed by VOLTE button
WHY we have to try different techniques like engineering mode or APN adding or other techniques every time.

OK if did those techniques by learning or searching is also appears HD symbol is some hours and it's went gone disappearing.
and again we have to DO that technique to repeat
in MOTOROLA and other android devices Sims of 4g are working flawlessly without the extra APS or EXTRA buttons simply connecting working no EXERCISES.

PLEASE FOCUS IT IS MAJOR ISSUE WHY BECAUSE MOBILES OR NOT ONLY FOR DATA PURPOSE THE MAIN PURPOSE IS primary USAGE
   "CONNECTING CALLS"
YOU ARE FORGETTING
THE
FLYME IS FORGETTING