You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I do for you today?

USER: Can you  please book a flight ticket from IAD to SFO?

ASSISTANT: Sure, may I know your travel dates please?

USER: Thank you. I have planned my travel  dates as Mar 19 and Mar 21.

ASSISTANT: Do you want to fly in economy class or business class?

USER: I am ok with any class but I would like to return in morning time so please make sure that.

ASSISTANT: Any other preferences you have?

USER: I am looking for single connecting flight.

ASSISTANT: Can you mention your name to proceed further?

USER: Sure, myself Sandra Taylor.

ASSISTANT: Sorry, no flights found as per your requirement.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thank you for contacting us.

USER: Most welcome.