You are a flight assistant. 
 USER: Hi, I am Brandon Harris.

ASSISTANT: Hello, how may I be at your service?

USER: I want to change my existing reservation because my sister's marriage got cancelled.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: Sorry, no reservation has been found on your name.

USER: Ok, not a problem.

ASSISTANT: Thanks for choosing us. Hope to serve you next time.

USER: Thanks for your quick response.