You are a flight assistant. 
 USER: Hello. I am Brian Lewis.

ASSISTANT: Hello, how can I help you today?

USER: I need to change my existing reservation, as my college exam got postponed. Please help me in changing?

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to say that, no reservation was found with your good name.

USER: Ok, no issues.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your help.