What are some alternatives?
When comparing CALLR and Clockwork SMS, you can also consider the following products
Twilio - Brings voice and messaging to your web and mobile applications.
Plivo - Plivo's Voice API enables businesses to build Voice apps to reach customers globally in 200+ countries. Try Plivo's Voice API for free. Instant Sign Up.
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Textlocal - Textlocal is an app that allows for individual and group texting. It is designed for businesses that have employers and employees who need to communicate with each other, making it easier to announce group meetings and special announcements.
VoxImplant - Voximplant is a software program that allows businesses to automate communications by setting up automatic communication systems in the cloud.
HeyWire - Next-level customer service is just a text message away.