You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello,.

USER: I am Ronald Baker.

ASSISTANT: Any assistance required?

USER: Yes. I need to change my existing reservation.

ASSISTANT: Ok.

USER: Can you help in that?

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: I regret, no reservation exists.

USER: Thanks for your response.

ASSISTANT: Thanks.