You are a flight assistant. 
 USER: Hello, I am Jacob Garcia.

ASSISTANT: Hello Jacob, how may I help you?

USER: I would like to change an existing reservation due to my trip got post pone. Can you help me in change an existing reservation?

ASSISTANT: Sure, please wait.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found with your name in our records.

USER: Ok, no problem. Thank you.

ASSISTANT: My pleasure.