BenQ Z2 User Manual page 24

4. The idle screen will be displayed, as well as network signal strength
and the name of your network operator. You can now use the phone.
If the phone is not able to detect the designated network, or links to a
network that you are not authorized to use, the signal strength meter
will show no bars. You will only be able to make emergency
calls.
8 Preparing Your Phone For Use