What are some alternatives?
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Twilio - Brings voice and messaging to your web and mobile applications.
Bandwidth - Track your Wi-Fi hotspot usage. Zero configuration required. It just works.
SendBird - SendBird is messaging-as-a-service.
Telnyx - Telnyx is a cloud-based platform that offers access to carrier grade voice services over the internet.
Pusher Chatkit - Developer-driven chat done simply.