Zabbix - Track, record, alert and visualize performance and availability of IT resources
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
openITCOCKPIT - openITCOCKPIT is a leading open source monitoring framework based on Naemon (Nagios). In addition it integrates Checkmk and Prometheus. It also offers interfaces to Icinga2, PRTG and opManager to obtain status and performance from them.
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
Nagios - Complete monitoring and alerting for servers, switches, applications, and services
HelpScout - Help Scout is a simple, straightforward way to provide excellent support