Usually you cancel appointments or meetings, not the people themselves.

Thanks, Kimberly. I just met the sentence from the book, Tuesdays with Morrie. And in that case, to cancel someone means to cancel the appointment. I don't see the structure very often, so I pose the question.

Pat McGibbon's answer is totally correct. Just to add, since it sounds like you want to be able to say something different than "to cancel an appointment"... if you are talking about, for instance, a situation related to social media where you don't want someone to be able to contact you, the phrase most commonly used is "I have already BLOCKED a lot of the people who (want to connect with me, for example)." I don't know if this is what you were trying to say. I hope it's helpful.