You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Donald Clark. I want to change my existing reservation. Can you help me in doing that?

ASSISTANT: Please wait a moment.

USER: Sure, take your time.

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

USER: Ok, no problem thank you for your help.

ASSISTANT: Thank you for reaching us.