You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, what can I guide you at this moment?

USER: I want to change my reservation due to health problem, can you help me?

ASSISTANT: I am here to help you about your flight ticket modification. Can you please provide your name so that it helps me to check the existing reservations under your name?

USER: Myself Mary Collins.

ASSISTANT: I am sorry to say this Collins, I am not able to find a existing reservations under your name to change. Most welcome, thank you for reaching out here. Hope you have a nice day ahead.

USER: No problem, thanks for checking.

ASSISTANT: You are most welcome.