You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: Can you help me to change my existing reservation?

ASSISTANT: Sure, may I know your name?

USER: I am Andrew Williams.

ASSISTANT: I have tried to drag your reservation states but unfortunately there is no active reservation on your name.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you so much for choosing us.