You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: My name is Donna Thompson.Could you help me make a plane reservation?

ASSISTANT: Sure, can you tell me source and destination details?

USER: My travelling codes are from DCA to ORD.

ASSISTANT: OK, could you please tell me travelling dates?

USER: Sure, my travelling dates are 10/18 and 10/20.

ASSISTANT: OK. Give me a moment.

USER: OK.

ASSISTANT: Sorry to inform you that there is no flight found matching your requirement. Thank you for reaching us.

USER: OK, that's fine. Thank you for assisting me.

ASSISTANT: OK. You are welcome.