Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Talkus - Chat with your website users from Slack
SendBird - SendBird is messaging-as-a-service.
Drift - A messaging app that helps you grow your business.
Aircall's Zendesk App - The best phone companion for Zendesk
Drift for Enterprise - Automatically turn website traffic into sales meetings