Grant is thinking of dropping his cellphone and just use Google Voice. Another option is Skype. Leo says that it could work if you use a mobile device that is data only. That's the biggest issue. Tello is one such service. But it depends on how much voice bandwidth you use, as after a set amount, Tello drops to 2G speeds. Voice takes 86kbps, and 2G is 100kbps. So it's possible.