Virtual Classroom Software Resources

I have a customer that needs a subscription to webex services: 5 employees would have access to schedule and manage meetings and 15 employees will be attendees only. The solution must include video conferencing, chat, desktop sharing and audio calls (VoIP and PSTN ). There are many webex solutions (webex meeting center, webex event center, webex connect..). I am confused and I do not know wich solution is appropriate to my case

What needs to be fixed or adjusted on my side so I can always hear all of the attendees in a meeting?

Our old conference call system used to have a way for us to type a conference call and meeting code into the Location field for meetings. Participants could tap that string of numbers on a mobile device, and they'd be placed in the meeting without having to enter a code manually. It was awesome, especially if you were driving and didn't want to be handling your phone much.