You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello,. How may I assist you?

USER: I am Patrick Turner. I want to do some change in the existing reservation because my friends are not able to come on those date, can you help me with it?

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: No reservation found for changing existing reservation.

USER: Fine, thanks for the information.

ASSISTANT: Thanks.