You can set your phone to select a network automatically or you can select a network manually. If you select a network manually, your phone will lose network connection when the selected network is out of reach.
Just so you know...
Please select the red text to see instructional images.
Select one of the following options:
Select network manually, go to 2a.
Select network automatically, go to 2b.
2a - Select network manually
If automatic network selection is turned on:
Press the indicator next to "Automatic" until the function is turned off.
Your phone searches for networks within range.
Press the required network.
Your display will tell you if you've access to the network you've chosen.
2b - Select network automatically
Press the indicator next to "Automatic" until the function is turned on.