Slow Internet. Overloaded Wi-Fi. Can't get anything but 2G connection on your phone. Voice calls turn into inaudible mess. Not for Zangi users. You can call your friends even if your phone shows that dreaded 'E' for network connection. Starting from only 8Kbps connection you will be able to make normal calls. Wherever you will go.
Check the graph below to see how much bandwidth Zangi uses compared to other big names.