You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: My name is Brian Perez. My holiday trip has been postponed, so I would like to change my existing reservation. Could you please help me with that?

ASSISTANT: Sure, let me check.

USER: Ok.

ASSISTANT: Sorry, I have not found any reservation under your name.

USER: That's ok. Thank you for the information.

ASSISTANT: Thank you for contacting us.

USER: You are welcome.