You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I am David Hall. Owing an emergency want to change my reservation, can you help me with it please?

ASSISTANT: Sure Hall, I am here to help you with this.

USER: Thank you.

ASSISTANT: Sorry Hall, there is no reservation found as per your name to change it.

USER: That's ok, thank you for the response.

ASSISTANT: You are welcome always.