What are some alternatives?
SendBird - SendBird is messaging-as-a-service.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
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.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
HeyWire - Next-level customer service is just a text message away.
Viber - Free and secure calls and messages to anyone, anywhere. Keep your conversations going no matter where you are.