Howdy @fac_arai ,
Thanks for sharing your question with us. It sounds like you might have a setting for you to be notified when someone joins your meeting room without you.
These instructions from Zoom might be helpful: Receiving email notifications when attendees join meeting before host – Zoom Help Center
If you want to maintain security of your room, you may want to select to have a waiting room and select that attendees can't log-in without the host. Just a suggestion.
Hope that helps,
Sky V. King, FIU Online