You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Charles Miller here.

ASSISTANT: How can I help you today?

USER: I would like to visit Philadelphia for a business meeting, can you please help me out with booking of a flight ticket to go there?

ASSISTANT: Sure, I will help you in booking flight ticket.

USER: Thank you.

ASSISTANT: Could you please mention your preferable airport code names?

USER: Sure, I want to travel from DCA to PHL.

ASSISTANT: May I know your travel dates for booking flight ticket?

USER: Sure, I am planning to leave on 04/26 and please book my return ticket on 04/28.

ASSISTANT: Please hold on a moment, I will check flight availability in this route.

USER: Ok, I will wait for your response.

ASSISTANT: Sorry for the inconvenience no flights available in this route as per your requested dates.

USER: Oh! So sad to hear that. Anyway, I will choose another alternative to go there. Thank you for the information.

ASSISTANT: Thank you for reaching us, have a nice day.

USER: Most welcome.