You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Sarah Harris, I want to book a flight from Washington DC to meet my friend at St. Paul. Can you book a connecting flight for me?

ASSISTANT: Let me know your travelling dates.

USER: I will fly on Mar 19 and return on Mar 20.

ASSISTANT: Can I know your airport codes?

USER: My source point is IAD and my destination is MSP.

ASSISTANT: Sorry, no flights found for your travelling dates.

USER: Ok, thank you for the information.

ASSISTANT: Thank you.