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.

Twilio - Brings voice and messaging to your web and mobile applications.

Telnyx - Telnyx is a cloud-based platform that offers access to carrier grade voice services over the internet.

Bandwidth - Bandwidth offers SIP trunking, Emergency communications, and Voice & Messaging APIs.

Plivo - Plivo simplifies your customer engagement.

Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates