There are a number of different possibilities. Each ISP needs to enable VoLTE. So searching Telstra, as an example, should list those phone models that Telstra supports. In fact by Googling various Telstra links you will find a number you can ring from your phone which will give you automatic feedback. Different isps approve different models.
Specs for your phone. My favourite specs site, gsmarena, is as bad as many other sites at listing whether VoLTE is included as a feature in the phone. Quite likely not. If a 2017 model - my previous Samsung J8, 2018, didn't have it until updated software around 2020.
Further problems if you have a grey market phone not sold by an authorised Australian retailer, e.g. not Kogan. It would be a different model and Australian updates wouldn t be available. There is a vaguely possible but no guarantee workaround if Samsung has supplied a software update to allow VoLTE on this model. A grey market model may also use different frequencies that affect coverage.
The lower priced Samsung models are reasonably priced. Secondhand models can be excellent subject to checking whether they have VoLTE and are not grey market phone models.
