You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I support you?

USER: I need to change my existing reservation, can you please help me with that?

ASSISTANT: Sure, please let me know your name.

USER: Patrick Miller.

ASSISTANT: Ok, please give me a moment to check the status and revert you.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found by your name in our data base.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for choosing us.