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, may I know your name please?

USER: John Harris.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, there was no reservation found with your given name.

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

ASSISTANT: Thank you for opting us.