You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Benjamin Adams. I want to change an existing reservation, due to my exams has been  postponed. Can you please change my reservation?

ASSISTANT: Sure, I am here to help you. Please wait a moment I will check your details and proceed further.

USER: Sure, take your own time.

ASSISTANT: Sorry to say, I did not find any details in my database regarding your reservation.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for choosing us, have a nice day.