You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I serve you?

USER: Donna Clark here, can you change my existing reservation to new dates?

ASSISTANT: Sure, I will help you with the change of flight reservation.

USER: Thank you.

ASSISTANT: Donna, just wait for a minute please. I will check with your details and get back to you.

USER: Sure.

ASSISTANT: Ok, thanks for waiting. But I am sorry to say that there is no reservation on your name.

USER: It's ok, thanks for checking.

ASSISTANT: Thanks for reaching to us.