WhatsApp Business - Communicate more efficiently with your customers
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
WATI - No-code chatbot builder for WhatsApp Business
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Sipdroid - Free and open-source SIP/VoIP Client