Hi @Welcomed ,
We do not have information on how to setup Telstra G2 modem/router but here are some article that you may use as a reference.
Using a third party modem, the VoIP phone service will not work.
You may contact the manufacturer of your own modem to guide you with the configuration. Make sure that the settings are correct and the modem is compatible with NBN service.
If you would like to configure your own modem, then you need to make sure that the settings are set as follows;
VLAN = 2
connection = VDSL PPPoE
username = firstname.lastname@example.org
password = TPG Password
Let us know should you require further assistance.
How long does it take to connect the phone light on a Telstra g2 modem from the TPG staff?