persuade somebody that something is not true
disabuse - correct
If you ‘disabuse’ somebody of something, then you convince or show them that what they think is in fact false. While that can be a good thing, there are occasions when people will do this erroneously in order to gain an advantage. You may often see or hear this term used in connection with words such as ‘notion’ or ‘idea’.
I erroneously thought that my boss had a personal problem with me, so I’m glad she took the time to disabuse me of that idea.
I used to think that John was a great guy, but after just a few days working together on the project, I was disabused of that notion.
My colleague did his best to disabuse me of my desire to apply for the vacant managerial position because he wanted it for himself.