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