You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello, may I help you?

USER: I am Ryan Lewis. I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: We found your reservation, can you let me know your new journey dates?

USER: Sure, 04/24 and 04/26 are my travelling dates.

ASSISTANT: May I know your airport codes, please?

USER: I need a flight ticket within 200. OAK and AUS are my airport codes.

ASSISTANT: Okay, wait a minute.

USER: Ok.

ASSISTANT: We found a flight on Spirit airline, flight number 1027 with the fare of 200. Shall I book it?

USER: You can reserve it.

ASSISTANT: Your ticket has been booked.

USER: Thank you.