You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Paul Garcia. Due to a urgent meeting, I want to change a existing reservation. Would you help me out?

ASSISTANT: Yes definitely, wait a minute.

USER: OK.

ASSISTANT: Sorry Paul, In my records I didn't found your reservation.

USER: That's OK.

ASSISTANT: Thank you.

USER: Thank you for your time.