You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Janet Carter here.

ASSISTANT: How may I be of your service?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, I'll help you in changing an existing reservation. Ok, please wait a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry to inform you that there is no reservation by this name.

USER: No problem, thank you.

ASSISTANT: Thank you for approaching us.