If you are a member of Choice I would also advise you to avail yourself of the Choice Help service. You can contact them via this web page:
https://www.choice.com.au/choice-help-form
Also make a complaint to your State’s Fair Trading Office and the ACCC (they may have more than a passing interest in this due to an older Enforceable Undertaking) as suggested by @meltam above, see this Choice article that includes the contact details:
Also some other useful Choice articles:
A handy pdf document of the ACL can be found here and page 19 of the document might be useful for you to print out and supply to Myer.
You may also be interested in the following article on the ACCC website regarding an Enforceable Undertaking entered into by Apple in 2013:
and the pdf of the actual undertaking:
