You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am William Thompson.

ASSISTANT: How can I serve you today?

USER: Please change my reservation due to post pone of my sister's engagement.

ASSISTANT: Sure. Please, wait.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no reservation found on your name.

USER: Fine, thanks for the information.

ASSISTANT: Thank you for choosing us.