You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: Can you please help me in booking my flight ticket from DCA to BOS?

ASSISTANT: Sure, I will help you with that. Can I have your travel dates please?

USER: My travelling dates are Aug 18 and Aug 20.

ASSISTANT: Do you have any requirements?

USER: I need to depart to my destination at the evening time. Can you please help me with that?

ASSISTANT: Sorry to say, there is no flight available for you as per your requests. May I know your name?

USER: Ok, fine thank you checking. Mean while my name is Frank Hall.

ASSISTANT: Thank you for reaching us.

USER: Most welcome.