You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I serve you today?

USER: I want to change my existing reservation due to postponed of my exams. Can you please help me with it?

ASSISTANT: Sure, I'll help you with this.

USER: Thank you.

ASSISTANT: Please let me know your name to check the reservation status.

USER: My name is Brandon Allen.

ASSISTANT: Ok, please wait a while.

USER: Sure.

ASSISTANT: Thank you for waiting, we did not found any reservation by this name.

USER: OK, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thanks for your information.