You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation, as my health is not good to travel. Can you please help me with this?

ASSISTANT: Yes I am here to help you, can you please mention your name?

USER: Sure, I am David Martinez.

ASSISTANT: David, you have no reservation to change.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for availing our services.