Hi @Job ,
The Home Phone Optional Prepaid Balance is $0 by default, to make an outgoing call that is outside your plan inclusions, you can top up from $10, $20, $100 and $200 to be able to use your home phone. When the prepaid balance is $0, you can only make calls to emergency service (000) and to TPG 13 14 23.
For more details please see the link below.
I still have $8.65 balance on my NBN digital voice service. Am I required to add $10 every month or can I wait till the balance is low before topping up?