You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you for now?

USER: I would like to change my existing reservation, due to health issues. Can you please help me?

ASSISTANT: Ok, may I know your name to check with your previous booking?

USER: My name is William Carter.

ASSISTANT: Ok, please be on hold for a while.

USER: Sure.

ASSISTANT: William Carter, there is no active reservation by your name. Thank you for choosing our agency.

USER: No problem, thank you for checking.

ASSISTANT: Have a great day ahead.