You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: May I know your name to check your reservation?

USER: Robert Roberts.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Thanks for waiting, I have gone through the reservation list twice but could not find any reservation active under your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Welcome Robert Roberts.