Fongo requires an internet connection to allow it to place/receive calls or send/receive texts. Since we use Voice Over Internet Protocol (VoIP) technology we need an internet connection (WiFi or 3G/LTE data connection).
The use of the internet connection allows us to bypass your carrier's cellular voice connection and thus their calling plan and rates. This in turn allows us to provide free calling through our own network instead of your carrier's.
Other internet based apps such as Facebook or Twitter also require an internet connection. You cannot update the feed on Facebook or Twitter without an internet connection.