If you have problems using network configurations on your phone, such as mobile data, Wi-Fi or Bluetooth, resetting the network settings may help.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press General management.
Press Reset network settings.
Please note that all saved APN, Wi-Fi and Bluetooth connections and passwords, you've created, are deleted.
Press Reset settings.
Press the Home key to return to the home screen.