Hi, the Australian tagging guidelines 
https://wiki.openstreetmap.org/wiki/Australian_Tagging_Guidelines/Australian_features
Shows the phone format should be 
+61 7 1234 5678 or
+61 456 789 123 for mobiles
For 1800 numbers…
phone:AU=1800 123 456
The spaces are used for readability.
More on the wiki link

 