Question: What happens when a served mobile subscriber, with the subscription option 'control of barring service: by service provider', attempts to register a new call barring password?
Option 1: The registration is successful, but the new password must be approved by the service provider before it takes effect.
Option 2: The attempt to register a new call barring password will be denied.
Option 3: The subscriber is prompted to contact the service provider for assistance with the registration process.
Option 4: The registration procedure redirects the subscriber to a different security protocol for enhanced verification.
Explanation: This outcome directly relates to the control mechanism chosen by the subscriber (or applied by default) at the time of service provision. When 'control of barring service: by service provider' is selected, it implies that the service provider retains authority over changes to the call barring settings, including password updates. Thus, any attempt by the subscriber to independently register a new password would be rejected to maintain the integrity of the service provider's control.