You can use the VoIP Plan to make calls. If you enable the plan, you will be given an 8-digit number so you can make and receive calls. The data that is expended on a voice call will be deducted from your monthly data allotment. Although making phone calls using your traditional handset won't be possible.
The requirement for a TPG VoIP connection, is that you'll require a compatible VoIP handset or softphone to make outgoing or receive incomming phone calls. Currently, there are hundreds of difference choices for VoIP handsets in the market, so don't be worried. Generally you'll pay between $40 - $200 depending on the type of handset you may require. e.g. wireless, hardwired, softphone.