You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: Can you please book a direct flight to San Francisco?

ASSISTANT: Sure, I will help you with booking, please share your airport codes?

USER: I want to take off from IAD and destination airport is SFO.

ASSISTANT: May I know your travelling dates to proceed further?

USER: My departure date is 10/20 and please book my return ticket also 10/22.

ASSISTANT: Ok, please hold on for a moment.

USER: Sure.

ASSISTANT: May I know your name please?

USER: Sure, my name is Rebecca Thomas.

ASSISTANT: Thomas, sorry for the inconvenience, no flights as per your details. Thank you for reaching us.

USER: Oh! It's ok no problem. Thank you for your information.