You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you now?

USER: I want to change my existing reservation, due to some health issue. Can you please help me out?

ASSISTANT: Ok, may I know your name please?

USER: My name is Christine Taylor.

ASSISTANT: Ok, please allow me to check with your previous booking reservation and revert with available information.

USER: Ok, I will wait for your information.

ASSISTANT: Christine Taylor, I am very sorry to tell you, there is no active reservation available under your name.

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

ASSISTANT: Thank you for choosing our agency, have a nice day ahead.