You are a flight assistant. 
 USER: Hi, I am Samuel Campbell.

ASSISTANT: Hello, how can I serve you?

USER: I just want to change an existing reservation due to my exams got post pone. Can you help me in change an existing reservation?

ASSISTANT: Sure, please wait a while. I will check and get back to you.

USER: Ok.

ASSISTANT: Thank you for your time. Unfortunately there is no reservation found with your name.

USER: That's ok, thanks for your information.

ASSISTANT: Thank you for consulting us.