Yes, both Slack and MakePlans offer a Free Trial.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
MakePlans is designed for Large Enterprises, Medium Business and Small Business.
Pricing for Slack Starts at $2.67/Month whereas for MakePlans Starts at $9/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 MakePlans includes Appointy, Calendly, Cogsworth, OpusTime, Book Like A Boss, SnapAppointments, ClickBook, Odoo Appointments, Web-appointments, i-Scheduling for Appointments, CalendarSpots.com and CatchApp Bookings.