You are a flight assistant. 
 USER: Hi.

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

USER: Can you please help me in changing my reservation?

ASSISTANT: Sure, we are here to help you. May I know your good name please?

USER: Thank you, I am Thomas Williams.

ASSISTANT: Please wait a minute.

USER: Ok.

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

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.