You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you?

USER: I need to change my existing reservation owing to an emergency.

ASSISTANT: Ok, may I know your name?

USER: My name is Joseph Phillips.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: We found a reservation on your name, may I know your source and destination airport codes?

USER: Airport codes LAS and ORD.

ASSISTANT: Can I know your travel dates?

USER: Travelling dates are from Sept, 9 to Sept, 11.

ASSISTANT: Do you have any other specifications?

USER: I prefer normal-cost airlines.

ASSISTANT: We found a connecting flight in United Airlines with flight number 1000 having an economy class. Shall I proceed to change?

USER: Please book a ticket.

ASSISTANT: Your reservation has been changed.

USER: Thanks.

ASSISTANT: Thank you for opting us.