You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I do for you today?

USER: My name is Kathleen Davis.

ASSISTANT: OK.

USER: I want to change my existing reservation due to postpone of my exam.

ASSISTANT: Ok, please wait. I will check your reservation.

USER: Sure.

ASSISTANT: Sorry, we did not find your reservation.

USER: No issue, thank you for your service.

ASSISTANT: Thanks for reaching us, have a nice day.