Don't have your land line number blocked for Caller ID, but need to make an anonymous call.  If you are with Telstra or Optus, just include the numbers 1 8 3 1 before the number you are calling.

Already have your land line number blocked, but want to allow your phone number to be identified for one call?  Include the numbers 1 8 3 2 before the number you are calling.

For mobile phones:

To restrict caller ID from being displayed on a call-by-call basis:  Include   #31#   before the number you are calling.

To display Caller ID on a call-by-call basis:  Include   *31#   before the number you are calling.