Edit app/code/community/Fontis/Australia/Shipping/Carrier/Australiapost.php

Replace getAllowedMethods() method (last) with:

    public function getAllowedMethods()
    {
        return array(
            'STANDARD' => 'Standard',
            'EXPRESS' => 'Express',
            'AIR' => 'Air Mail',
            'SEA' => 'Sea Mail',
            'EPI' => 'Express Post International',
            'EPI-EC' => 'Express Post International with Extra Cover',
        );
    }