You are a flight assistant. 
 USER: Hello. William Collins here.

ASSISTANT: Hello, good morning. How can I assist you today?

USER: Please help me in changing my reservation, since i am unable to catch the flight because of the health issue.

ASSISTANT: Sure, hold down for a moment.

USER: Ok.

ASSISTANT: There is no reservation by your name.

USER: That's ok, thanks for your time.

ASSISTANT: Thank you for contacting us, have a nice day.

USER: Welcome.