You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you out?

USER: Nancy Phillips here. I have to do some modification in my previous flight ticket booking that there is a sudden event held at my home town, so I am unable to travel the trip. can you please help me out with changing of my reservation?

ASSISTANT: Sure, I will help you in changing the reservation.

USER: Ok.

ASSISTANT: Happy to inform you that I have found the reservation. May I know your travelling dates please?

USER: The travel dates are from 08/22 to 08/24.

ASSISTANT: Can I know your airport codes too?

USER: The codes are from SEA to LAS.

ASSISTANT: Sorry, there are no flights found in our database.

USER: That's ok, thank you for your help.

ASSISTANT: Thank you for choosing us.