You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: As my leave got extended, I want to change my existing reservation. Can you help me out?

ASSISTANT: Sure, I will help you to change your reservation. May I know your name to check your previous reservation.

USER: Sure, my name is Joseph Carter.

ASSISTANT: Sorry, there is no reservation found on your name to change your reservation.

USER: That's fine, thank you for the information.

ASSISTANT: Welcome. Thank you for checking.