You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Catherine Smith here. I want to modify my previous reservation. Can you please help me for that?

ASSISTANT: Sure, please be on hold.

USER: Ok, I will wait.

ASSISTANT: There is no reservation found under your name to do modifications.

USER: Anyway, thank you for the information.

ASSISTANT: Thank you for choosing us.