Prevent candidate from selecting two interview slots

Summary:

We have had an issue where a candidate has selected an interview slot but can no longer make it. Instead of cancelling and rescheduling, they have gone in and selected a second slot meaning the manager has two interviews for the same candidate in their diary

Content (required):

Is there a setting to prevent this?

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):