Yes, both Slack and Unily offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Unily is designed for Large Enterprises and Medium Business.
Pricing for Slack Starts at $2.67/Month whereas for Unily Starts at $4,995/Month.
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 Unily includes Interact, Interact Software, Invotra, MyHub Intranet Software, Beezy, Oak Engage, Axero Intranet and Engynn Intranet.