You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you today?

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

ASSISTANT: Sure, please wait for few minutes.

USER: Ok.

ASSISTANT: There is no existing reservation found on your name in our data base.

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

ASSISTANT: Thank you for reaching us.