Asterisk - An open source telephony switching and private branch exchange service for Linux.
ProTexting - ProTexting offers mobile marketing tools for businesses to communicate with their audience via SMS & MMS campaigns.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
ShoutOUT - All in one business texting tool to send personalized alerts, promotions, reminders, short links and marketing campaigns, for any SMEs (hotels, restaurants, education, non profits, Woocommerce, banks, healthcare, agencies, supermarkets, weddings)
Wazo.io - The UCaaS Platform Built for MSPs
Trumpia - SMS Marketing and Marketing Automation software for Mass SMS, internal communications & emergency alerts. #1 Text Messaging Service used by Fortune 500s.