You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Melissa Moore.

ASSISTANT: How may I help you? Nice to meet you Melissa.

USER: Due to health issue, I need to change my existing reservation. Please help me in that.

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

USER: No problem, thanks for your information.

ASSISTANT: Thank you.