You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Mark Campbell.

ASSISTANT:  How can I help you now?

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

ASSISTANT: Sure, we are here to help you, can you please  share your travelling dates?

USER: My travel dates are 05/19 and 05/21.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Sorry Mark Campbell, there is no flight found as per your travelling dates.

USER: No problem, thanks for checking.

ASSISTANT: Thank your for reaching us.