Yes, both Slack and Zenduty offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Zenduty is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Zenduty Starts at $5/User/Month when Billed Yearly.
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 Zenduty includes Freshservice, PagerDuty, Opsgenie, VictorOps, AlertOps, Spike.sh, Rootly, Incident.io, StatusCast Incident Management, PagerTree and ResQ.