You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be your helping hand?

USER: I am Melissa Green. I want to change my existing reservation. Could you help me?

ASSISTANT: Sure, I am here to help you. Please wait for a while, I will check your reservation.

USER: OK.

ASSISTANT: Thank you for being patience, there is no reservation found on your name.

USER: That's ok, no problem. Thank you for helping me.

ASSISTANT: Thank you for contacting us.