You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Melissa Lee here.

ASSISTANT: How can I assist you?

USER: Can you change my existing reservation?

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Sorry Lee, there is no reservation found on your name.

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for approaching us.