Yes, both osTicket and Zendesk Support offer a Free Trial.
osTicket is designed for Individuals, Large Enterprises, Medium Business and Small Business.
Zendesk Support is designed for Large Enterprises, Medium Business and Small Business.
Pricing for osTicket Starts at $9/User/Month whereas for Zendesk Support Starts at $19/user/month when yearly.
Some top alternatives to osTicket includes Zoho Desk, Zendesk Support, ManageEngine ServiceDesk Plus, Freshservice, Jira Service Desk, Freshdesk, HelpDesk, SysAid, UVdesk, Jitbit Helpdesk, eStreamDesk, ReadyDesk, Spiceworks Help Desk, HESK, BoldDesk and GLPI.
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.