You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am William Taylor.

ASSISTANT: How could I help you?

USER: Can you help me in changing my recent reservation, as my exam is postponed?

ASSISTANT: Please wait for a while.

USER: Ok.

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

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for opting us.