YouMail - YouMail turns visual voicemail into a personal assistant for handling all your missed calls.
Video SDK from Zoom - Build fully customizable video-based apps
MightyCall - Virtual phone system that lets you run your business from anywhere.
Amazon Chime - Online meetings and video conferencing
Grasshopper - Grasshopper enables entrepreneurs to build a virtual office that connects callers to employees, wherever they are.
AuthKey.io - SMS API and WhatsApp Business API