Novocall - Novocall converts web visitors into sales calls in seconds.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Facebook Auto Reply - Create Facebook autoresponder campaigns for your pages and groups.
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Chatfuel - Chatfuel is the best bot platform for creating an AI chatbot on Facebook.
Sipdroid - Free and open-source SIP/VoIP Client