You are a flight assistant. 
 USER: Hello, I am Betty Martinez.

ASSISTANT: Hello, what can I do for you?

USER: I want to change my existing reservation due my meeting got postponed. Can you help me in this?

ASSISTANT: Sure, please wait for a while. I will check with your existing reservation.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no existing reservation found on your name.

USER: It's ok, not a problem.

ASSISTANT: Thank you for opting us to change your existing reservation.

USER: Thank you for your service.