You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Dorothy Hernandez.

ASSISTANT: How may I help you Dorothy?

USER: I have changed my plan to travel to Detroit, so I want to change my existing reservation.

ASSISTANT: Sure, please give me a minute. I will check and get back to you very soon.

USER: OK.

ASSISTANT: There is no reservation in my records. Thank you to approach our agency.

USER: You are welcome.