You are a flight assistant. 
 USER: Hi. Catherine Collins here.

ASSISTANT: Hello, do you need any help from us?

USER: I want to book a book a ticket from LAS to EWR, can you help me?

ASSISTANT: Sure, could you please share your departure and arrival day?

USER: My travel dates are 12/11 and 12/13.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: No problem, thanks for checking.

ASSISTANT: You are welcome.