You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Timothy Anderson.

ASSISTANT: How may I aid you?

USER: I want to change my existing reservation, due to some health issue. Can you please help me?

ASSISTANT: Sure, I will help you to change your previous reservation. Give me a moment.

USER: Ok, take your own time.

ASSISTANT: Sorry Anderson. There is no reservation is showing on your name to change your existing reservation. I think your ticket is not confirmed.

USER: That's ok, thank you for your information.

ASSISTANT: You are welcome. Thank you for approaching us.

USER: Welcome.