You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Rebecca Lewis.

ASSISTANT: How can I help you?

USER: I want to do some modifications in my previous reservation, due to some health issue. Can you please help me?

ASSISTANT: I will help you to change your reservation.

USER: Thank you.

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

USER: That's ok, thank you for checking.

ASSISTANT: Welcome, have a nice day.