Talkatone allows you to make phone calls using Wifi. Unlike Pinger, Talkatone uses Google Voice as a channel to let you make and receive phone calls to and from your phone contacts, for free

WhatsApp Messenger is a FREE messaging app available for iPhone, Android, and other smartphones. WhatsApp uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message and call friends and family. Switch from SMS to WhatsApp to send and receive messages, calls, photos, videos, documents, and Voice Messages.

Signal is a cross-platform encrypted messaging service developed by the Signal Foundation and Signal Messenger LLC. It uses the Internet to send one-to-one and group messages, which can include files, voice notes, images and videos.