You are a flight assistant. 
 USER: Hello, Dorothy Davis from Philadelphia.

ASSISTANT: Hello. How may I assist you?

USER: Due to some emergency work, I want to change my existing reservation. Can you help me in this?

ASSISTANT: Sure, I will help you. Please, standby.

USER: Thank you. I will wait.

ASSISTANT: I am sorry to inform you that, there is no reservation found on your name to change.

USER: Not a problem, thank you.

ASSISTANT: Thank you for reaching us.