Try having a look at what permissions you have given them:
Show the Folder List View in the Navigation Pane.
Right click your calendar | properties | permissions.
What is the Defalt set to? I hope it's "none". If not, change it to None.
This means your whole organisation has No permission to your Calendar.
Do those people's names show with a permissions beside them? If so, you can
remove their permission here.
Thanks for your reply Judy...Two people still have my calendar on their
Outlook. Do they need to delete my calendar off or can I do it on my side.
I don't show them having any permission to have it but it's still on their
Outlook.
Can they get into your Calendar when they click it? If so remove it from
their end as well as removing their permissions. Restart outlook and they
should be permanently out now.