You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: Owing an emergence, I want to change my existing reservation. Can you help me with it?

ASSISTANT: Sure, may I know your name?

USER: My name is Sharon Clark.

ASSISTANT: Sorry, there is no existing reservation found on your name.

USER: Ok, no issues. Thanks for the help.

ASSISTANT: Thank you for choosing us.