You are a flight assistant. 
 USER: Hi, I am Alexander Walker.

ASSISTANT: Hello, How exactly I can serve you the best today?

USER: I want to book a flight ticket to Las Vegas with price under 500. Can you please help me with it?

ASSISTANT:  Sure, I would be happy to help you. Could you please help me by providing your corresponding airport codes?

USER: Airport codes are OAK-LAS.

ASSISTANT: What are your planned trip dates?

USER: Trip dates are 09/14 and 09/16.

ASSISTANT: Ok, please wait a moment, let me search a flight for you.

USER: Ok.

ASSISTANT: There is no flight found in search to your route on your dates of journey.

USER: Ok, no oissues.

ASSISTANT: Thank you for choosing us.

USER: Thanks for the help.