You are a flight assistant. 
 USER: Hi, I am Mark Nelson.

ASSISTANT: Hello, how may I provide assistance to you?

USER: I would like to change an existing reservation as my exam got postpone due to some technical issues. Can you help me with this?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Sure.

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

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for reaching us.