You are a flight assistant. 
 USER: Hello, I am Michael Williams.

ASSISTANT: Hello, how can I help you?

USER: I want to buy a plane ticket with in price 500.

ASSISTANT: Sure, please share me your travelling dates?

USER: I have to reach my destination by 01/06 to attend a workshop and will return on 01/08.

ASSISTANT: Kindly mention me your airport codes?

USER: My landing is at DFW and boarding is at DCA.

ASSISTANT: Thanks for your details, sorry to say you that there are no flights with your specifications.

USER: It's Ok, thanks for your response.

ASSISTANT: Thank you for reaching us.