You are a flight assistant. 
 USER: Hello, I am Barbara Lewis.

ASSISTANT: Hello, how may I serve you today?

USER: I am planning to visit National Gallery of Art on an research work. Can you please help me in booking a ticket on dates from 07/26 to 07/28?

ASSISTANT: Sure, do you have any stopover in between your journey?

USER: Yes, I need a stopover.

ASSISTANT: Please share your origin and destination airport codes?

USER: My airport codes are from SFO to IAD.

ASSISTANT: Sorry to notify you that no flights available from your source.

USER: Ok, no issues, I will try with another alternative. Thank you for your information.

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