You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I assist you at this moment?

USER: Can you please help me to change my reservation?

ASSISTANT: I am happy to serve you about your query.

USER: Thank you.

ASSISTANT: Could you please provide your name for checking the reservation status with your name in our booking list?

USER: My name is Charles Robinson.

ASSISTANT: I apologise to say this Charles Robinson, there is no active reservation with your name in our booking list.

USER: Thank you for informing me.

ASSISTANT: You are welcome, thank you for choosing us. Hope you have a nice day ahead.