Kannel - Open Source WAP and SMS Gateway
MessageBird Voice API - Add programmatic call capabilities to your app or service
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
MessageBird Chat API - Connect with your customers through different messaging apps
Bulk SMS Services - Sending Bulk SMS to the customers will engage the customers with your business and new offers.
MessageBird API on StdLib - Purchase numbers, send SMS and more with one line of code