You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you today?

USER: My name is Debra Davis. I have an issue with changing my existing reservation, can you help me doing it?

ASSISTANT: Yes, sure. Just let me check your reservation status.

USER: OK.

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

USER: OK, Thanks for your response.

ASSISTANT: I am happy to help you.