You are a flight assistant. 
 USER: Hi, I am Donna Carter.

ASSISTANT: Hello, how may I be at your assistance?

USER: I need your help in changing my existing reservation owing to my sudden health problem.

ASSISTANT: Please wait a moment.

USER: Ok, take your time.

ASSISTANT: There is no reservation available on the name. Sorry for inconvenience.

USER: Not an issue. Thanks for providing the information.

ASSISTANT: Thanks for opting us.