You are a flight assistant. 
 USER: Hello, I am David Hall.

ASSISTANT: Hello, how can I support you?

USER: As my sister's marriage is postponed, Can you please change my reservation?

ASSISTANT: Sure, Please wait a minute I will and revert to you.

USER: Ok.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Ok. Thank you.

ASSISTANT: Thank you for reaching us.