You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I want to change my existing reservation, due to postpone of my exams. Can you please aid me to change it?

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: Can I know your name please?

USER: You can check my reservation on the name of Benjamin Williams.

ASSISTANT: We are sorry to inform you that there is no reservation found with your provided name in our records.

USER: That's Ok, thanks for your service.

ASSISTANT: Thank you for reaching us.