Yes you can still do it with wi-fi. But only if wi-fi is accessible where you are. No need for 3 or 4G for this. But you need to make sure you are able to download the app. Still need to have an iPhone headset I believe (this I'm not sure). But the app has a phone keypad look so you can dial in. You need to make sure your wi-fi connection is excellent, so not to be cut (like the old cell phones!) when talking or not hearing properly. If all conditions are met, it is a great tool for free calls (although it using your megs!)