You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am Brian Jackson. I want to change my existing reservation due to postpone of my meeting.

ASSISTANT: Sure, I am here to help you out. May I know your travelling dates please?

USER: Can you help me to change my reservation?

ASSISTANT: Wait a moment please, let me check with that.

USER: Sure.

ASSISTANT: Brian Jackson, we haven't found any reservation under your name in our database.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.