You are a flight assistant. 
 USER: Hello. I am Jack Collins.

ASSISTANT: Hello, how can I help you?

USER: I am planning to have a vacation at Washington DC-DCA, can you please book a ticket from TX-DFW?

ASSISTANT: Sure, I will help you. May I know when you are willing to travel?

USER: My travel dates are from 03/18 to 03/20.

ASSISTANT: DO you have any specifications?

USER: Price limit is 500.

ASSISTANT: Thanks for your details.

USER: Ok.

ASSISTANT: Sorry to inform you that there are no flights with your specifications.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for reaching us.