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 Wireless & networks.
Tap Mobile network.
Tap Preferred network mode.
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.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.