You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I serve you now?

USER: Please change my existing reservation. I am Sarah Lopez.

ASSISTANT: Sure, I will help you to change the reservation. Please wait for a moment, while I check for the reservation.

USER: Ok.

ASSISTANT: Thanks for holding, there is no reservation found on your name.

USER: Thanks.

ASSISTANT: Thank you for reaching us.