You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I want to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Sure, can I have your name to check with the details.

USER: My name is Dennis Johnson.

ASSISTANT: Please wait a moment.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry, there are no active reservations on your name to change.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for reaching our service.