You can set your mobile phone to find a network automatically or you can choose a network manually. If you select a network manually, the network connection will be lost if you're out of range of the selected network.
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Tap the indicator next to "Automatic" to turn automatic network selection on or off.
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If you turn off the function, tap the required network (eg. Singtel Mobile).
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Return to the home screen
Slide your finger upwards starting from the bottom of the screen to return to the home screen.