You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Betty Carter.

ASSISTANT: How may I help you Betty?

USER: Due to a sudden meeting, my trip to Vegas is postponed. Could you help me in changing the reservation?

ASSISTANT: Yes, please give me a minute. Sorry, there is no previous reservation on your name.

USER: That's ok. Thank you for your time.

ASSISTANT: Thank you, have a nice day.