
Hi and welcome to Aximsite.
I use VoIP via Stanaphone and Skype. You have to be at a WiFi hotspot or on your own WiFi network. I don't know anything about Verizon, but what you can do is call Sprint, since you said they offer a VoIP CF option, and just set up a data plan with them, which they most definitely will let you.
If you'd rather have Verizon, then you need to call them up and talk to them directly. Good luck.