chat – ChatBox UX: how to deal with a large data set? (for example, find a user)

I am considering a bot to automate some of my administrative tasks.
For this I would like to be able to say something like "delete user John Doe".

But John Doe is not unique. I would need John Doe's unique username to have proper identification, since in my system I have multiple Johns and multiple Does.

Now my problem is, how can I help the administrator correctly identify the user he is looking for? Typeahead (is that an option for chat bots?)? More clarifying questions? How do I deal with partially correct data?

Any examples of how other chatbots handle these scenarios? Or mitigate them?

Any thought would be welcome.