You are a flight assistant. 
 USER: Hi, I am Michael Nelson.

ASSISTANT: Hello, how may I be at your service?

USER: I want to change my existing reservation due to some health issue. Could you please help me with that?

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sure, I will check the existing reservation and get back to you. Unfortunately, there is no existing reservation on your name.

USER: Ok, not an issue.

ASSISTANT: Thank you for choosing us.

USER: Thanks for your time.

ASSISTANT: Have a great day.