Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Raaft - Reduce SaaS churn
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Cancelo.io - Cancelo helps you save more customers with customized cancelation flows
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
ProsperStack - Subscriber retention done right.