Twilio - Brings voice and messaging to your web and mobile applications.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.
Nextiva - Business VoIP, cloud phone systems trusted by more than 150,000 companies. Powered by the leading cloud PBX VoIP platform, Nextiva is rated the best business VoIP service provider.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Genesys Cloud - As the foundation of great customer experience, the Genesys PureCloud contact center platform empowers your business to provide excellent service across the entire customer journey.