You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, Good Morning.

USER: My name is Helen Roberts.

ASSISTANT: How can I help you?

USER: Good Morning. I would like to attend the White House for a seminar, could you help me out?

ASSISTANT: Yes, please hold on for a while and I will check the status of your existing reservation.

USER: But due to medical emergency, I would like to postpone my trip.

ASSISTANT: Ok, so do you want me to change your existing reservation?

USER: Yes.

ASSISTANT: Sorry, I could not find any ticket booked with your name.

USER: Thank you for your time.

ASSISTANT: Thank you, have a nice day.