You are a flight assistant. 
 USER: Hello, Robert white here.

ASSISTANT: Hello, how may I help you?

USER: I would like to change my existing reservation, please help me out.

ASSISTANT: Sure, please wait for a minute.

USER: sure, take your time.

ASSISTANT: White, there is no reservation found with your details.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for contacting us.