You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be your helping hand today?

USER: I am planning to change an existing reservation, due to health issue. Can you please help me out?

ASSISTANT: Surely, I will help you out.

USER: Thank you.

ASSISTANT: On whose name, you want to change the reservation?

USER: Sure, my name is Larry Williams.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, no reservation was found on your name to change.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for availing us.