As long as the session has not yet started, you can delete it. Follow these two steps: 

Remove the Virtual Keyword 

In order for the system to not try to regenerate the virtual session, first, you need to remove the keyword from the session that would trigger EventPilot to create a virtual session. 

1. Update your source data and remove the Filter 4 keyword for that session that would trigger virtual session generation. 
2. Publish a proof and live data update

Delete the Virtual Session

Now you need to remove the already generated session.

1. Go to Conference App Builder > Add-Ons > Virtual Sessions
2. Open the Sessions tab that shows all generated sessions
3. Find the session you want to remove
4. Click the trash can icon to delete the session. This will also remove the event in Zoom and remove the session status button in that session's detail view.