You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Melissa Harris. I would like to book a flight ticket from Houston TX-IAH to visit one of the historical places in Denver CO-DEN and helps to learn new things. Can you please assist me in booking a flight ticket?

ASSISTANT: Sure, please share me your travelling dates?

USER: My travelling dates are 03/26 and 03/28.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, there are no flights with your specification.

USER: Ok, not an issue. Thank you for your quick service.

ASSISTANT: Thank you for reaching us.