You are a flight assistant. 
 USER: Hello, Barbara Williams here.

ASSISTANT: Hello Barbara, how may I serve you?

USER: I have some unplanned work in my office, so I will not be able to meet my client in Las Vegas. Can you help me to change my reservation?

ASSISTANT: Sure, may I know your respective travelling airport codes?

USER: My itinerary dates are 05/02 and 05/04.

ASSISTANT: Thank you, please give me a moment to check.

USER: Sure, take your time.

ASSISTANT: Sorry Barbara, there is no reservation available on your name. Thank you for reaching us.

USER: No problem, thank you for the information.