Hi @stevieg . This page is for D7800 on BYO router data only plan, and FTTP, and Superfast/Ultrafast for FTTP and HFC. All these plans do not use VLAN ID.
If you are on bundled NBN/VOIP plan even if you don't use the phone, VLAN ID=2 is needed. This iiNet article shows how to set VLAN ID=2 for FTTC and HFC.