Welcome to the Community!
I've managed to locate your account and have seen that you have been assisted by a member of our Accounts Team.
It appears that your pre-payment has gone below the minimum amount. The initial $20 pre-payment is charged at point of sign up to cover the costs of any calls that may be made from the service. All TPG NBN plans are offered to customers as a pre-paid bundle of Internet & Home phone.
As the line we are connecting will be capable of being used as a standard home phone service, the pre-payment will act as a reserve for any calls made that are not included in your bundle selection. If you choose not to make outgoing calls, then this payment will remain intact with no further payment made towards your monthly service charges.
Let us know should you require further assistance.