You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I assist you?

USER: I am Brenda Lopez. I want to change my existing reservation as my exam got rescheduled. Please help me out.

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: I have checked all the reservation list I could not find any reservation with your name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.