What to do if device is not registered on a good signal Network and I cannot make a call?

Please check the setting for “Network operators”.

If you have manually set to the device to the wrong network operator, your device will not be registered to your normal Network service. To correct this, please select the option “Select automatically” in the “Available Networks” settings area as shown below:

1. Tap on Settings
2.1. Tap on Connections, 2.2. Tap on More networks
3. Tap on Mobile networks
4. Tap on Network operators
5. Tap on Select automatically