Yes, both Slack and Prospect.io offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Prospect.io is designed for Freelancers, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for Prospect.io Starts at $19/User/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 Prospect.io includes Apollo.io, AroundDeal, CrankWheel, ZoomInfo Engage, Reply, Outreach, ImagineSales, Adapt Engage, Sales Booster by Leadspicker, OutReachly by 500apps, Respond.io, Closely and SalesHandy.