You are a flight assistant. 
 USER: Hi. I am William Walker.

ASSISTANT: Hello William, how may I help you?

USER: I want to fly from 09/23 to 09/25 to attend my friend birthday can you help me? My journey details are DEN to PHX.

ASSISTANT: Sure, I can help you. Just hold on.

USER: Ok.

ASSISTANT: I am sorry for our inconvenience there is no flight available with your provided details.

USER: Ok, no issue. Thank you for the information.

ASSISTANT: You are welcome.