Voxbone - Fully compliant, enterprise-ready voice and SMS on demand. Build local presence on a global scale with elastic SIP trunks and phone numbers. Try for free.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Twilio - Brings voice and messaging to your web and mobile applications.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.