You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you?

USER: I want to change my existing reservation in the name of Charles Collins. Can you help me in this?

ASSISTANT: May I know your name?

USER: Already mentioned.

ASSISTANT: Sorry, please wait a minute.

USER: Ok.

ASSISTANT: There is no reservation on your given name.

USER: It's ok, not an issue. Thank you for your information.

ASSISTANT: Thank you.