Call-in User X represents an unidentified telephone connection into your meeting. To avoid it, you have to help Webex match that audio connection with the correct name in the Participant Panel.

Cause: When a caller dials in to the audio conference using the I will call in option, they will be prompted to enter the Access code into their phone. At this point, every caller in your meeting looks the same to the Webex server. Then the server asks the caller to enter his unique Attendee ID into their phone. The Attendee ID is only available on the screen after the caller joins the web portion of the meeting. If the caller does not enter their unique Attendee ID, the Webex server does not recognize who the attendee is and it will connect the attendee into the meeting as Call-in User X.

Some ways to avoid having Call-in User X:

• Ask the caller to hang up and dial back in, keying his Attendee ID into the phone when prompted to do so.
• Ask the caller to hang up, and key his phone number in to the screen to receive a call back from the Webex server.
• Ask the caller to hang up and join via VoIP.

See the following article on how to:Prevent Unwanted People from Attending Your Meetings.