my phone m31 not supported dual volte

[Anikroyale]

Contact your SIM service provider and ask them to enable VoLTE on your SIM.

[Ehsank]

if other sim supported, its auto visible in notification bar may not available in settings separately but it will showing in bar

[UzzuBhai]

if problem solve then on my comment right side click on 3 dots and accept my solution