There may be different network modes available depending on where you are. The network mode influences the data speeds your mobile phone can achieve.
Tap Mobile Data.
Tap Mobile Data Options.
Tap Voice & Data.
Tap the required network mode.
There may be different network modes available depending on where you are. If you set your mobile phone to the fastest network mode, it will always find the network with the highest data speed and best signal.
Tap the indicator next to "VoLTE" to turn the function on or off.
You can use 4G for voice calls via the mobile network for a faster and better connection. To turn VoLTE on or off, you need to select 4G (LTE) as network mode.