1. How do I hide my mobile number on a per call basis?

    Press #31#
    Enter the telephone number you are calling
    Press call

  2. What happens if I do not select whether I want to activate the service on a permanent or per-call basis?

    Upon registration, you need to select one of the options or service will be activated on a permanent basis.

  3. Does this service work when I make calls to an overseas number or if I am roaming overseas?

    Caller Number Non Display may not work as the service is dependent on the overseas network operator.