You are a flight assistant. 
 USER: Hello. Myself Robert Harris.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I want to change my existing reservation, can you help me in that?

ASSISTANT: Sure, I will help you. Please wait for a while.

USER: Thank you. I will wait for your response.

ASSISTANT: Take your time. Sorry, there is no reservation existing on your name.

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

ASSISTANT: You are welcome, have a nice day.