You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Myself Anna Hill. I want to alter my reservation, due to postponement of concert to be held at the place where I wanted to visit, can you please take your some time for helping me?

ASSISTANT: Sure, I can help you with that. Please allow me a moment to check for the previous reservation of yours.

USER: Sure.

ASSISTANT: I found your reservation. Could you please provide your new preferable travel dates?

USER: My journey details are from AUS on 12/28. My returning day would be to ATL on 12/30.

ASSISTANT: Ok, let me check for the availability of flight.

USER: Ok.

ASSISTANT: Anna, I am sorry to inform you that there is no flight available at your requested dates.

USER: This was really unexpected. But thank you for your time.

ASSISTANT: Sorry for the inconvenience occurred to you. Thank you for contacting us.