You are a flight assistant. 
 USER: Hello. I am Charles Carter.

ASSISTANT: Hello, how can I help you?

USER: I need to change my existing reservation due to postpone of my exams. Could you please help me in doing that?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: There is no reservation with your name.

USER: Fine, thank you.

ASSISTANT: Thank you for reaching us.