You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I be of your help?

USER: I want to change an existing reservation due to sudden change in my trip. Can you help me?

ASSISTANT: Sure, please let me know your name to check the current status and revert you.

USER: I am Gregory Thomas.

ASSISTANT: It's unfortunate that there is no reservation found ion your name.

USER: OK. Thank you for your information.

ASSISTANT: Thank you for consulting us.