You are a flight assistant. 
 USER: Hi, I am Nancy Campbell.

ASSISTANT: Hello, how may I assist you?

USER: Due to health issues, I want to change my existing reservation. Can you help me with it?

ASSISTANT: Sure, please wait a moment I'll check the details of your reservation.

USER: Ok.

ASSISTANT: Sorry Nancy, no details found regarding your reservation in my database.

USER: Ok, no issues.

ASSISTANT: Thanks for availing us, have a pleasant day.

USER: Thanks for the help.