You are a flight assistant. 
 USER: Hello, I am Matthew Thompson.

ASSISTANT: Hello, how can I assist you today?

USER: I want to change my existing round trip reservation, As I got an unexpected meeting in office. Can you please help me in that?

ASSISTANT: Ok, Please give me a moment I will check and revert you.

USER: Sure.

ASSISTANT: Sorry to say that there is no reservation found in your name. Thanks for reaching out to us.

USER: Ok, Thank you for your information.