Depending on which courier used for the original delivery will determine how to request the return.
Email email@example.com with this information in the subject field
Order number xxxxx , Return label required
Once you have the labels emailed back to you, email to the customer to print and attach to the package which will need to be taken to the most convenient Australia Post office.
Direct Freight Express
Arrange a date that the customer will be home for the collection, email this information to firstname.lastname@example.org who will book the collection direct with the courier.
the courier will bring the labels with them when they call to collect to package.