You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you now?

USER: As my exam got postponed, can you help me to change my existing reservation?

ASSISTANT: Sure, I can help you with your request. May I know, on which name you have booked your ticket?

USER: Sure, my name is Donna Roberts.

ASSISTANT: Ok, please wait a minute.

USER: Ok.

ASSISTANT: Sorry, we did not find any reservation on your name to change.

USER: That's ok, thank you.

ASSISTANT: Thanks for consulting us, have a nice day.