You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Sarah Evans.

ASSISTANT: How may I assist you at this moment?

USER: Can you help me to change my reservation?

ASSISTANT: Sure, I will help you with that. Please wait a moment to check your previous reservation.

USER: Ok, take your time.

ASSISTANT: We regret to inform you that there is no reservation found on your name in our records.

USER: That's ok, thank you for your help.

ASSISTANT: Thank you for reaching us, have a great day.