You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Ok, I will help you with that. Can you please provide your name to check for existing reservation?

USER: My name is Larry Carter.

ASSISTANT: Hold on a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, we found a reservation on your name. Can you please share your planned journey dates?

USER: Departure is Mar, 1 and return date is Mar, 3.

ASSISTANT: May I know your take off and landing airport codes?

USER: Airport codes IAD and LAS.

ASSISTANT: Let me know your connection preference.

USER: I prefer connecting flight.

ASSISTANT: Do you have any other requirements?

USER: I would like to depart in the morning time.

ASSISTANT: Give me a minute, please.

USER: Sure.

ASSISTANT: Thank you for your time. I am sorry to inform, there are no flights available that matches your requirements.

USER: Thank you.

ASSISTANT: Thank you for approaching us.