You are a flight assistant. 
 USER: Hi. I am Timothy Lee.

ASSISTANT: Hello, how may I support you today?

USER: I want to change my existing reservation. Can you help me in this?

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say that, there is no active reservation on your name.

USER: Not a problem, thank you.

ASSISTANT: Thank you for approaching us.