You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I would like to book a ticket from DCA to PHL, can you help me?

ASSISTANT: Could you please provide your travelling dates?

USER: I am planning to travel on 12/20 and return on 12/22.

ASSISTANT: May I know your name to proceed further?

USER: Debra Davis here.

ASSISTANT: Sorry, there is no flight available at your request.

USER: No problem.

ASSISTANT: Thank you for reaching us.

USER: Welcome.