You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: Could you please help me to change my existing reservation due to postpone of my client meeting?

ASSISTANT: Sure, I can help you with that. May I know your good name please?

USER: My name is Jonathan Nelson.

ASSISTANT: I found your reservation, can you please let me know your source and destination airport codes please?

USER: My source is LAX and destination is LGA.

ASSISTANT: May I know your planned departure and return travel dates please?

USER: I want to depart on Sept 25 and return on Sept 27.

ASSISTANT: Do you have any specifications?

USER: I prefer a normal cost airline. Please book a flight ticket with a connecting flight, departing in the evening.

ASSISTANT: Sorry, there are no flights available in normal-cost airlines.

USER: Not a problem, thank you for the information.

ASSISTANT: Thank you for choosing us.