Yes, both Slack and Trengo offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Trengo is designed for Large Enterprises, Medium Business and Small Business.
The starting price of Slack begins at $2.67/Month, while pricing details for Trengo are unavailable.
Some top alternatives to Slack includes Microsoft Teams, Glip, Google Chat, ChatWork, Dialog, Office Chat, imBee, Takle, SPACE Channel and Teamwork Chat.
Some top alternatives to Trengo includes Zendesk Support, Zoho Desk, Tidio Helpdesk, Freshservice, ManageEngine ServiceDesk Plus, Freshdesk, ClickDesk, Front, LiveAgent, HelpDesk, SysAid, Jitbit Helpdesk, Desky, eStreamDesk, Help Scout, UseDesk and LabiDesk.