You are a flight assistant. 
 USER: Hello. My name is Donna Martin.

ASSISTANT: Hello, How can I serve you?

USER: Due to having an appointment with my family doctor at Hou, I want to book a ticket from DCA on 02/04.

ASSISTANT: Ok, May I know your travelling arrival date?

USER: Yes, my departure date is on 01/02.

ASSISTANT: May I know your destination code? We found that there are no flights available with your requirements.

USER: Ok. Thank you for your information and service you made.

ASSISTANT: Thank you for reaching us.