You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you for the day?

USER: I am Barbara Hall. Due to health issue, I need to modify the dates of my existing reservation. Can you help me?

ASSISTANT: Sure, I will check the reservation on your name and get back to you.

USER: Ok, take your time.

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

USER: Ok fine. Thank you for your information.

ASSISTANT: Thank you for availing us.