Have you ever been totally certain about something, but later changed your mind about it? How did that happen? Was it through conversation, an experience, something that you lived through? What was that process like for you?
Have you ever changed someone else’s mind? Why did you feel compelled to do that? Was it intentional?

What do you let go of when you change your mind? What do you gain?

Also, if you want to be more literal about this prompt, you could literally change their mind: a brain transplant, a software upgrade, a mind meld… interpret this idea in any way you like.