Etihad Airways complaint: Refund for a failed business class upgrade

On 10th of March I bid for a business class upgrade for my flight EY460 from Abu Dhabi to Melbourne on 14 March 2023. The funds (AU$ 2910) were taken out of my bank account however the upgrade was not processed in time for my flight on 14th of March, 2023 and I flew in economy class. I contacted Etihad Airways several times since 15th of March 2013. I was told that refund is being investigated. I was asked to send my boarding pass and extract from my bank, yet still no refund. The interaction with customer service has been frustrating. Every time I call Etihad I am being asked the same questions again and again and no one gives me any reference or complaint number. Every time Etihad acts like it’s a first time I’m lodging a complaint. There were no update or any follow up attempts to contact me even though my phone and email were requested by Etihad customer service. I’m not sure what I can do in this situation.