You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: Timothy Roberts here. I would like to visit Minneapolis, can you help me to book a flight ticket from IAD to MSP?

ASSISTANT: Can I have your trip dates?

USER: My trip dates are 12/15 and 12/17.

ASSISTANT: Thanks for your details, please wait a minute.

USER: Sure.

ASSISTANT: Sorry Timothy Roberts, there is no flight found with your preferences.

USER: Thanks for your valuable information.

ASSISTANT: Welcome Timothy Roberts.