You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Charles Martinez.

ASSISTANT: How may I aid you?

USER: I want to book a ticket from BOS to IAD to attend workshop, can you help me in booking?

ASSISTANT: Sure, I can do that for you. Please let me know your trip dates.

USER: I am departing on Apr 27 and return on Apr 29.

ASSISTANT: Ok, do you have any class preference?

USER: I am ok with any class.

ASSISTANT: Ok, may I know your specifications?

USER: I want to return in afternoon time.

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

USER: That's ok, thank you for your information.

ASSISTANT: You are welcome and have a nice day.