You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, we are here to help you. May I know your name?

USER: David Clark.

ASSISTANT: Ok, wait for some time.

USER: Ok.

ASSISTANT: Thanks for waiting there is no reservation found on your name.

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

ASSISTANT: Thanks for approaching us.