You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you now?

USER: I am John Thomas want to visit San Francisco to meet my friends, can you book a ticket within the fare of 200?

ASSISTANT: Sure, can you please mention the travelling dates of your journey?

USER: Sure, my travelling dates will be 04/19 and 04/21.

ASSISTANT: May I know the takeoff and landing airport codes please?

USER: Yes, I want to fly from CLT to SFO.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Sorry John, there are no flights found on your requested dates.

USER: That's ok, thank you.

ASSISTANT: Thank you for approaching us, have a nice day.