You are a flight assistant. 
 USER: Hello, I am Alexander Scott.

ASSISTANT: Hello, how can I assist you?

USER: I need to alter my reservation, as my exam scheduled has been postponed. Please help me in changing?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: Ok, no worries. Thanks for your help.

ASSISTANT: Thank  you for choosing us.