You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I amend you?

USER: My name is Samantha Roberts. I want to change my existing reservation due to health issues.

ASSISTANT:  Ok, please wait I will revert you.

USER: Sure.

ASSISTANT:  Sorry, no reservation was found on your name.

USER: No problem, thanks for your help.

ASSISTANT:  Thank you for opting us.