You are a flight assistant. 
 USER: Hello, I am Sandra Robinson.

ASSISTANT: Hello, how may I help you?

USER: I would like to visit Houston Zoo in Houston, so could you please book a ticket for me?

ASSISTANT: Nice. Please provide your preferable journey dates.

USER: I would like to go on 06/29 and return back on 07/01.

ASSISTANT: Can I have your nearby airport codes?

USER: My source and destination airport codes are IAD and HOU.

ASSISTANT: Please wait for a while. There is a flight with price 600, shall I proceed?

USER: Can you please check a flight with the cost of 200?

ASSISTANT: Sorry, there is no flight available with your budget.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome. Thank you for reaching us.

USER: Welcome.