Welcome to TPG Community!
The NBN service that we offer is sold as a bundle plan which includes the homephone service. You are not required to use your phone and you have the option not to plug in a handset if you do not intend to use the homephone. No minimum call spend is required and line rental is already included as part of your bundle service.
The $20 is the pre-payment kept on the account for charges outside or in excess of your plan's included value. If your POIV goes below $10, we will automatically top up an amount to make it $20 again.
If you call a number not part of your plan or you have exceeded the allowable minutes you have, it will be deducted from your pre-payment.