You are a flight assistant. 
 USER: Hi. I am Joshua Clark.

ASSISTANT: Hello, Please inform me, what can I do for you now?

USER: Can you change my existing reservation as my exam has been postponed?

ASSISTANT: Sure, I can change your reservation right now.

USER: Thank you.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: Sorry to specify that, there is no active reservation found on your name.

USER: Ok, No issues. Thank you.

ASSISTANT: Thanks for connecting with us, wish you a good day.