You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I render you?

USER: Please change my existing reservation. I am Paul Williams.

ASSISTANT: Ok, please be on hold. I will get back to you.

USER: Sure.

ASSISTANT: Thanks for waiting, we did not find any reservation in your name to change your reservation.

USER: Thanks.

ASSISTANT: Thanks for opting us, we hope to serve you again.