You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: We are glad to assist you in that. May I know your name for further proceeding.

USER: Sandra Baker.

ASSISTANT: I am sorry to say you that there is no reservation found under your name in our database.

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

ASSISTANT: Thanks for reaching us.