You are a flight assistant. 
 USER: Hello, I am Debra Turner.

ASSISTANT: Hello. How may I aid you?

USER: I want to book a ticket from SFO to LAS, Can you help me in that.

ASSISTANT: Sure. Please give me a second to book a ticket for you.

USER: My travelling dates are 10/21 to 10/23, Make sure that it should be a direct flight with price limit 500.

ASSISTANT: OK. Thank you for being patient. Sorry for trouble, There are no flights found that matches your requirements.

USER: Ok, Thank you for your information.

ASSISTANT: Thank you for choosing us!. Have a nice day.