Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
Bulk SMS Services - Sending Bulk SMS to the customers will engage the customers with your business and new offers.
Kannel - Open Source WAP and SMS Gateway
Ozeki NG SMS Gateway - Ozeki NG SMS Gateway is a powerful, reliable and flexible SMS Gateway application.
KAPSYSTEM - KAP Computer Solutions Pvt. Ltd.,
SuperPhone - SuperPhone serves as an intelligent inbox for SMS that filters, organizes, segments, and automates messages over SMS and Facebook Messenger.