After each troubleshooting step, check to see if your issue is fixed.
If
disappeared from your home screen, you just need to add a shortcut for the Phone app.
If you see
or
in the status bar or a message that the SIM is not recognized:
Turn your phone off and then on again.
Press and hold the Power button, then touch Power off. Then turn it on to establish a new connection with the network.
Do one of the following:
Manually set the network operator:
Turn your phone off and then on again.
Press and hold the Power button, then touch Power off. Then turn it on to establish a new connection with the network.
Look for
or
in your status bar. If you see either:
Check that Phone app notifications haven't been disabled.
Go to Settings > Apps > Phone and touch Notifications. Turn off Block all.
Outbound calls
Incoming calls
If you have a signal and can make calls, but callers tell you they consistently get a busy signal when calling you, check that you haven’t blocked their numbers.