You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I would like to change my existing reservation, due to postpone of my meeting. Could you please avail me in changing?

ASSISTANT: Sure, may I know your good name please?

USER: Sharon Roberts here.

ASSISTANT: Sorry, there is no reservation found on your name in our database to change.

USER: Ok, not an issue.

ASSISTANT: Thank you for reaching us.

USER: Thank you for your response.