You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Sharon Martin. I am planning to change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Please wait for a moment.

USER: Sure, I will wait for your reply.

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

USER: That's fine. Thank you for your service.

ASSISTANT: Most welcome.