You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: May I know if it is possible to change my existing reservation as I can not make journey due to health issues?

ASSISTANT: Sure, please share your good name?

USER: Katherine Roberts here.

ASSISTANT: Please wait for a while.

USER: Take your sufficient time.

ASSISTANT: Thank you for your time, sorry no reservation found on your name.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for choosing us.