You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I want to travel from DCA to LAS. Can you please help me with the booking?

ASSISTANT: Sure, may I know your name?

USER: Myself Donna Allen.

ASSISTANT: When do you want to travel?

USER: I want to travel on July 27 and intend to return on July 29.

ASSISTANT: Do you have any other preferences?

USER: Yes, I need a connecting flight with an economy class.

ASSISTANT: May I know your good name, please?

USER: Already mentioned above.

ASSISTANT: Sorry, there are no flights available on your travelling dates.

USER: Ok, no problem. Thank you for the information.

ASSISTANT: Thank you for choosing us.