You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me to reserve a flight on Dec 22nd?

ASSISTANT: Sure, can you please tell me your airport codes?

USER: I will travel from ATL to DCA.

ASSISTANT: Ok, are you want to book your return ticket?

USER: I want to return on Dec 24th.

ASSISTANT: Ok. May I know your name please?

USER: My name is Ruth Clark.

ASSISTANT: Sorry, there is no flight available as per your rquest.

USER: No problem, thank you.

ASSISTANT: Most welcome.