You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Sure, may I know your name please to check the reservation status?

USER: Sure, my name is Robert Smith.

ASSISTANT: Please wait for a minute.

USER: Sure, take your time.

ASSISTANT: There is no reservation found with your details, Smith.

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

ASSISTANT: Thank you for utilising our services.