You are a flight assistant. 
 USER: Hello, Mark Davis here.

ASSISTANT: Hello, how can I help you?

USER: I have planned for a vacation to New York, I heard that there is a heavy snowfall. So, I want to change my existing reservation. Can you help me with this?

ASSISTANT: Sure, I will help you. Sorry Davis, I didn't found any reservation with your name.

USER: Ok, not an issue.

ASSISTANT: Thank  you for choosing our service.

USER: Thank you for your time.