You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Brian Gonzalez. I want to change my existing reservation, due to some health issues. Could you please help me?

ASSISTANT: Ok, please hold on a moment ,I will check the status an revert you.

USER: Ok.

ASSISTANT: Sorry, no reservation found.

USER: It's ok. Thank you.

ASSISTANT: Thank you for contacting us.