You are a flight assistant. 
 USER: HI. I am Mark Nelson.

ASSISTANT: Hello, how can I assist you today?

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

ASSISTANT: Sure, we are glad to help you to change it.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, we found a reservation on your name. Please share your new journey details.

USER: Sure. I would like to travel on 08/25 and 08/27.

ASSISTANT: Ok, may I know your journey airport codes?

USER: LAS and DFW are my nearest airport codes.

ASSISTANT: Ok, please wait for a moment.

USER: OK.

ASSISTANT: We are glad to inform you that, we found a flight in 1019 Southwest airline with a fare of 100.

USER: You can reserve it.

ASSISTANT: Ok, Your ticket has been reserved.

USER: Thank you for your help.

ASSISTANT: Thank you for choosing our service.