You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I support you for the day?

USER: I want to change my existing reservation as my appointment with my doctor is postponed.

ASSISTANT: Ok.

USER: So, please change my existing reservation.

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Let me know your name to check reservation.

USER: Sure, my name is Cynthia Martinez.

ASSISTANT: Please, hold on for a while.

USER: OK.

ASSISTANT: Thank you for waiting. We found a reservation with your name. Please, share your new travelling dates.

USER: Sure, my new travelling dates are 01/05 and 01/07.

ASSISTANT: Can I know your airport codes of journey?

USER: Sure, Atlanta, GA - ATL is my source airport code and Denver, CO - DEN is my destination airport code.

ASSISTANT: Do you need a connecting flight?

USER: Yes, I need a flight with single connection.

ASSISTANT: Thank you for waiting, there is a flight available with JetBlue airline, flight number 1018 with fare 100 and a lay by. Shall I proceed?

USER: Perfect, please proceed now.

ASSISTANT: Your reservation has been successfully changed.

USER: Thanks a lot, I am happy with your service.

ASSISTANT: Thank you for contacting us.