You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I support you?

USER: Please could you change my existing reservation.

ASSISTANT: Sure, we are here to help you. May I know your name to check your details?

USER: I am Sharon Lopez.

ASSISTANT: Ok, let me check. Sharon Lopez, we have found a reservation on your name. Please provide me your new journey details.

USER: Sure. Please book a ticket from Oakland, CA-OAK to Denver, CO-DEN.

ASSISTANT: What are your journey dates?

USER: Departure date is 01/26 and 01/28 is return date.

ASSISTANT: Ok, please wait a moment. We have a connecting flight at a fare of 300 in Spirit airline from flight 1001. Shall I proceed?

USER: Please book a ticket.

ASSISTANT: Your booking has been done.

USER: Thanks.

ASSISTANT: Thank you for choosing us.