I have found through personal experience that the way to get action is to contact the relevant ombudsman. This has worked for me when on the wrong end of a dispute with Telstra, plus two other smaller companies. On each occasion passing the information that the ombudsman had or would be called brought an immediate, almost magical change in attitude. After the ombudsman was called Telstra went from "we can't do anything", to "free calls & line rental for your small business for 12 months", + the deal I signed up for honoured. This was over 10 years ago when they were still a monolith.
Direct from the ASX website is the contact details for the Financial Services ombudsman.
Financial Ombudsman Service GPO Box 3 Melbourne Vic 3001