You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I would like to change my existing reservation, please help me out.

ASSISTANT: Sure, I am here to help you. Hold on for a moment. Let me check.

USER: My name is Debra Harris.

ASSISTANT: Ok. Sorry Debra, there are no flights reserved on your given name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.