You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I am Sandra White. I would like to travel from IAH to LAS, can you please help me to book a flight ticket?

ASSISTANT: Sure, can you please tell your travelling dates?

USER: I planned to travel on 06/21 and 06/23.

ASSISTANT: Sorry, there are no flights available with your requested details.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you and have a nice day.