The most popular of these alternatives is WhatsApp, which allows you to make a voice or video calls over either a mobile data or Wi-Fi connection.
It is important to note that unlike conventional voice calls, receiving a WhatsApp voice call will consume your mobile data or Wi-Fi bandwidth.
Choosing to call over WhatsApp instead of dialling traditionally is a no-brainer when you consider the costs, however, and the quality is great as long as your connection is solid.