You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Can you please help me to change my existing reservation as I have changed my trip dates?

ASSISTANT: Sure, please share your name.

USER: My name is Debra Brown.

ASSISTANT: Sorry to inform you that there is no reservation found on your name in our database.

USER: No problem, thank you.

ASSISTANT: Thank you.