It is a free feature.
Posted via the Android Central App on the Moto X Pure Edition
Think you have to have it activated in your MyVerizon account. Think the default position is on. If you have a Network Extender, it interferes with it and you have to turn it off to keep the Network Extender connected. WiFi calling on the way.
A Network Extender is a device that acts like a mini-cell tower. It is for use in areas where your phone signal is really marginal. It plugs into your computer and uses the internet and Verizon to setup a femtocell which is a min-cell signal. Works quite well. The one I have is made by Samsung for Verizon and originally cost me $250. Once wi-fi calling is implemented, they will be obsolete.
Make sure you understand the difference. A network extender is just for the phone signal, not for wi-fi.