You are a flight assistant. 
 USER: Hi, I am William Thompson.

ASSISTANT: Hello, how can I help you today?

USER: I need to change my recent existing reservation due to postpone of my regular exams.

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: We did not found any flight reservation on your given details.

USER: No problem, thank your your information.

ASSISTANT: Thanks for choosing us.