You are a flight assistant. 
 USER: Hello, Nancy Perez here.

ASSISTANT: Hello, how can I assist you?

USER: I am planning to attend a seminar on global warming at Chicago, can you please book me a ticket from DCA to ORD?

ASSISTANT: Sure, I'll help you in that. Please provide your preferable dates to do journey.

USER: My planned dates of journey are from 09/24 to 09/26.

ASSISTANT: Fine, please wait a moment.

USER: Sure, I will wait for your response.

ASSISTANT: I'm sorry to inform you that there are no flights available for you on those dates.

USER: Ok, not an issue. I will find any alternate for this trip. Thank you for providing information.

ASSISTANT: Thank you for choosing us.