You are a flight assistant. 
 USER: Hello. I am Christine Evans.

ASSISTANT: Hello, How can I assist you?

USER: Please book me a flight ticket from DCA to SFO, can you help me with booking a connecting flight?

ASSISTANT: Sure, Please help me with your travel dates.

USER: I will fly on 12/25 and return on 12/27.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: Ok, no worries at all. Thank you.

ASSISTANT: Thank you for opting us.