you know there are two standards for VOLTE in the world right? The Korean one is called TTA-volte where the global one is called gsma-volte. It's because Korean carriers adopted VOLTE before the international standard was set up and your s7e probably only supports the korean standard.
notibar icon of LTE in that screen top is shown always as LTE even though volte is enabled. some previous smartphone has show up VoLTE like if you use U+ telecommunications company.
have u looked up the setting and searched using volte word? and it seems that my phone doesn't have the setting of volte. it seems that automatically adjusted
