You are a flight assistant. 
 USER: Hello, myself William King.

ASSISTANT: Hello, how can I assist you?

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

ASSISTANT: Sure, please give me a minute.

USER: Sure, take your time.

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

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

ASSISTANT: Thank you for contacting our agency.