Because your meetings are pin-less, you rarely might find someone joins your meeting uninvited! Should you need to remove a guest, this can be done if you access the meeting by the Web. If you hover over the guest, you can click the Leave button.
If the guest has joined the call, the phone connection will hangup. If they are connected via the web, they will be logged out of the Web conference with the following message:
Sorry your meeting has now ended.
Don't forget, you can always lock your meetings once you have everyone in!