You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am Dorothy Thompson. I want to do some changes in my existing reservation because I did not get the concert tickets, so planning to travel on another date, can you please help me?

ASSISTANT: Sure, can you please provide your new dates?

USER: I am planning travel from AUS to DEN, can you help me out? My travelling dates are 10/27 to 10/29.

ASSISTANT: Sorry, there is no flight available at your requested dates.

USER: That's fine.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your help.

ASSISTANT: Have a great day.