You can use Wi-Fi as an alternative to the mobile network when establishing an internet connection. This way your phone doesn't use mobile data.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press Wi-Fi.
Press the indicator next to "Wi-Fi" to turn on the function.
Press the required Wi-Fi network.
Key in the password for the Wi-Fi network and press the confirm icon.
If the Wi-Fi network is password protected, a lock icon is displayed next to the name of the Wi-Fi network. You can get the password from the network provider or administrator.