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

ASSISTANT: Hello, how can I help you?

USER: I want to change existing reservation, can you please help me with that?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

ASSISTANT: Sorry, there is no reservation with your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.