Users can join Webex meetings from anywhere using VoIP (Voice over IP) from any internet connected device, or using dial-in numbers with paid plan in many countries. Webex allows to host unlimited meetings with all the plans. 

Free version of Teams provides unlimited chat, video calling, storage and many other features. You can use the Teams free version as long as you want. 

Full version of teams with this offer supports up to 300 users for small and medium businesses. It includes Unlimited chat messages and search and Built-in audio and video calling for individuals, groups, and the team. It also provides 10 GB file storage for the Teams users and 2GB personal storage for each person. 

With Teams full version, users can collaborate in real time by leveraging the integration with Office apps for web including Word, Excel, PowerPoint, and OneNote plus 250+ business apps. 

This free trial offer is from ConferenceCalls.com, a global conference call service provider.
• Connect up to 50 Participants
• Use any phone such as offices, cell phones, pay phones to join a conference
• Dial in via toll-free and local numbers in 45+ countries
• Crystal clear conference call sound quality
• No prior reservation needed to start a global conference call
• No connection fees, No hidden fees
• Record your conference call on-the-fly to listen later
• No purchase necessary to try the FREE conference call offer

Zoom specializes in video conferencing, which is a form of a conference call in which video conferencing, online meetings, chat, and mobile collaboration can be combined.