You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Carolyn Moore.

ASSISTANT: How can I serve you for the day?

USER: Due to my health problem I want to change my existing reservation, can you please help me to change my reservation?

ASSISTANT: Sure, we are happy to help you. Please wait for a while. I will check and revert you.

USER: Sure.

ASSISTANT: Thanks for waiting, we are sorry to inform you that, there is no active reservation on your name to change.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for opting us.