You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation, due to some health issue. Can you please help me out?

ASSISTANT: Sure, may I know your name please?

USER: My name is Samantha Perez.

ASSISTANT: We found a reservation with your given name, please share your new journey dates.

USER: My journey dates are Mar 04 and Mar 06.

ASSISTANT: May I know your source and destination airport codes?

USER: My travelling airport codes are DTW to DFW.

ASSISTANT: Do you want connecting flight?

USER: I need a direct flight.

ASSISTANT: Do you have any other requirements?

USER: I want to return in evening.

ASSISTANT: Sorry, there are no flights found with your given details.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for opting us.