From the invite participants button, there should be an option to send a direct message to a company team member, and/or the ability to call their extension.
Currently, the option to call by phone does access my contact list or allow me to enter a fellow team members extension. If I use the desktop app to call them, or they call me, there has to be an easy way to merge or move that call to an existing meeting.
Case example. I am hosting a screen share (or video meeting) with someone. I want to invite a colleague to this meeting. If I send an email invite, I don't know if they are available. If I call them (or they call me), to have them join the current active video meeting, I have to message them the meeting info, they must hang up then join the meeting. I would prefer to be able to merge the voice call to the current video meeting.