Now that you might be working outside the office more, and are using your mobile phone as you don’t have access to your company phone system, you may not want your mobile number to be displayed (caller ID) – especially if using your personal mobile for business reasons. You could simply turn off your caller ID function on your mobile but rather than turning off caller ID permanently for all calls, you can do this per call (choose who sees your number and who doesn’t).
For Optus mobile – dial 1831 before the phone number you are calling to block your number
For Telstra and Vodafone mobile dial #31# before the phone number you are calling to block your number