You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I am Stephen Lee. Due to some inconvenience caused, I would like to change my existing reservation. Can you help me with that?

ASSISTANT: Sure,please wait a moment.

USER: Sure.

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

USER: No problem.

ASSISTANT: Thank you.

USER: Thank you for your response.