You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Can you help me to change a reservation which I had done on the name Helen Walker?

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

USER: Ok, please take your own time. Thank you for the positive response.

ASSISTANT: Sorry Helen Walker, there are no flights reserved on your given name formerly.

USER: Ok, that is not a problem. Thank you for choosing our agency.

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