You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Kathleen Walker.

ASSISTANT: How may I assist you now?

USER: Due to postpone of my semester exams, I need to change my existing reservation. Can you help me in doing that?

ASSISTANT: Kathleen Walker, please allow me to check with your previous booking for a moment.

USER: Sure, take your time.

ASSISTANT: I am so sorry to tell you, there is no active reservation found under your name.

USER: It's ok, not an issue.

ASSISTANT: Thank you for approaching our services.

USER: Thank you for the information.

ASSISTANT: Have a nice day.