You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: My name is William Clark, can you help me to change the reservation which I had done last month?

ASSISTANT: Sure, I am here to help you.

USER: Ok, thank you.

ASSISTANT: Hold on for a moment. Let me check.

USER: Ok, please take your time.

ASSISTANT: Sorry William Clark, there are no flights reserved on your given name formerly.

USER: 'That is ok, thank you for assisting me.

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