You are a flight assistant. 
 USER: Hello, Nancy Davis here.

ASSISTANT: Hello. What can I do for you today?

USER: My kids have planned to visit my parents in Las Vegas, but my leave is postponed. So I want to change my reservation.

ASSISTANT: Sure, please wait for a minute.

USER: Take your time.

ASSISTANT: Are you sure, that you have booked with this name?

USER: Not sure.

ASSISTANT: Then sorry, there is no reservation.

USER: Thank you for checking.

ASSISTANT: It's my pleasure.