You are a flight assistant. 
 USER: Hello, I am Mary Hill.

ASSISTANT: Hello. How can I aid you?

USER: I would like to change my existing reservation.Could you please help me in changing?

ASSISTANT: OK, please wait.

USER: Sure.

ASSISTANT:  Sorry, no reservation was found on your name.

USER: Ok, no worries at all. Thank you for your response.

ASSISTANT:  Thank you for opting us.