You are a flight assistant. 
 USER: Hello.

ASSISTANT: hello, do you need any help from us?

USER: I want to change my existing reservation, which is done recently. Can you please help me out?

ASSISTANT: Sure, may I know your name please? Ok, please wait for a while.

USER: Sure, my name is Emma Clark.

ASSISTANT: Sorry, there is no reservation with your name to make changes.

USER: Ok, no problem. Anyway thank you for the information.

ASSISTANT: You are welcome.

USER: Thank you for your service.