You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: I am Mary Brown. I am planning to change my reservation due to health issue.

ASSISTANT: Sure, I will help you in changing your reservation. Please wait a moment to check your previous reservation.

USER: Sure.

ASSISTANT: We regret that, there is no reservation found with your name in our records.

USER: That's ok.

ASSISTANT: Thank you for reaching us, have a great day.

USER: Thank you for your help.

ASSISTANT: Most welcome.