You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Donna Clark.

ASSISTANT: How can I assist you at this moment?

USER: I want to change my reservation, can you help in that?

ASSISTANT: Sure, I will help you with that. Please wait a moment and I will check your reservation.

USER: Sure.

ASSISTANT: Sorry Donna Clark, no reservation has found under your name to change.

USER: That's ok. Thank you for your help.

ASSISTANT: My pleasure. Thank you for choosing us, have a good day.