You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. May I know how best I can help you today?

USER: I am planning to change an existing reservation, due to health issue. Can you please help me out?

ASSISTANT: Sure, I'll try to help you in changing an existing reservation. Could you please let me know your name to check the reservation list?

USER: Thank you. My name is Margaret Martin.

ASSISTANT: Thank you for providing your name, please wait a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, Sorry there is no active reservation have been found under your name in our database to amend it.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for approaching us.