There may be different network modes available depending on where you are. The network mode influences the data speeds your mobile phone can achieve.
Slide your finger downwards starting from the top of the screen.
Tap the settings icon.
Tap Mobile networks.
Tap Preferred network type.
Tap SIM1 preferred network.
Tap the required network mode.
There may be different network modes available depending on where you are. If you set your mobile phone to automatic network selection, it will always find the network with the highest data speed and best signal.