You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. Welcome to our service!.

USER: My name is Angela Allen. I need your help in booking a flight ticket from LAS to ATL.

ASSISTANT: Your dates please.

USER: Sure, my departure date is on 06/21 and the return date is on 06/23.

ASSISTANT: Sorry Ms. Angela , on this dates flight is not going.

USER: That's OK. Thank you for checking. Have a great day.

ASSISTANT: Your most welcome.