Yes, both HelpDesk and Zendesk Support offer a Free Trial.
HelpDesk is designed for Large Enterprises, Medium Business and Small Business.
Zendesk Support is designed for Large Enterprises, Medium Business and Small Business.
Pricing for HelpDesk Starts at $29/User/Month when Billed Yearly whereas for Zendesk Support Starts at $19/user/month when yearly.
Some top alternatives to HelpDesk includes Zoho Desk, Zendesk Support, ManageEngine ServiceDesk Plus, Freshservice, Freshdesk, SupportBee, Teamwork Desk, SysAid, Jitbit Helpdesk, Snappy, Helpspot, ReadyDesk, HelpdeskEddy, Help Desk Premier, Support.cc by 500apps and BoldDesk.
Some top alternatives to Zendesk Support includes Zoho Desk, ManageEngine ServiceDesk Plus, Deskero, Support Hub, HelpDesk, Desky, Help Scout, Salesforce Service Cloud, ReadyDesk, Sitehelpdesk, HESK and BoldDesk.