You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello,. How may I help you?

USER: My name is Pamela Miller and I want to change my existing reservation.

ASSISTANT: Sure, I will check and revert you back.

USER: OK.

ASSISTANT: Thank you for waiting. Sorry, there is no reservation found on your name.

USER: OK, thank you.

ASSISTANT: Thank you for contacting us, have a good day.