I can't make voice calls

The selected network mode is not available

Turn on automatic network mode selection.

1 of 7 steps Slide your finger downwards starting from the top of the screen.
2 of 7 steps Press the settings icon.
3 of 7 steps Press Mobile networks.
4 of 7 steps Press Network mode.
5 of 7 steps Press the required network mode.
6 of 7 steps Press the Home key to return to the home screen.