You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I am Justin Campbell want to visit SFO, can you book a ticket from LAS?

ASSISTANT: Sure, can you please share me with your dates of travel?

USER: Sure, my travelling dates will be 04/26 and 04/28.

ASSISTANT: Please wait for a mean while.

USER: Ok.

ASSISTANT: Sorry Justin, there is no flight found as per your travelling details.

USER: That's ok, thank you.

ASSISTANT: You are welcome, have a safe flight.