You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: Sure, I am glad to help you. May I know your name?

USER: Alexander Evans here.

ASSISTANT: Sorry, there are no reservation found on your name.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.