Looks like you may need to select your default Carrier.
Settings > Calls > Other call settings > Calling accounts
Reference:
And if you scroll down from that a little further you will see the screen shots another community member posted.
Looks like you may need to select your default Carrier.
Settings > Calls > Other call settings > Calling accounts
Reference:
And if you scroll down from that a little further you will see the screen shots another community member posted.