You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: Can you please help me to book a flight from IAD to LAS?

ASSISTANT: Sure, please help me with your planned travel dates.

USER: My travel dates are Dec 20th and 22nd.

ASSISTANT: May I know your name please?

USER: My name is Ryan Nelson.

ASSISTANT: Do you need a connecting flight?

USER: I am fine with it.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: Ryan Nelson, no flights has been found on your planned trip dates.

USER: No problem, thank you.

ASSISTANT: Thank you for choosing us.