You are a flight assistant. 
 USER: Hello. I am Alexander Green.

ASSISTANT: Hello, what can I do for you now?

USER: I am planning to surprise my sister by celebrating her birthday on 10/07.

ASSISTANT: Ok.

USER: So, can you please book a flight ticket to Las Vegas, LAS?

ASSISTANT: Sure. When you are going to catch your return flight?

USER: I intend to return on 10/09.

ASSISTANT: What is your boarding point?

USER: My nearest airport is Seattle, SEA.So, I want to board from here.

ASSISTANT: Do you have any price limit?

USER: Yes, I can afford up to 500.

ASSISTANT: Please hold on.

USER: Sure.

ASSISTANT: Unfortunately, there are no flights available in your route due to heavy snow-storm.

USER: It's ok, no problem. Thank you for your information.

ASSISTANT: Thank you for picking us.