You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I render you today?

USER: I need to change my existing reservation as my college function got postponed, Can you please help me with that?

ASSISTANT: Sure, I am here to help you. May I know on whose name the ticket has been reserved formerly?

USER: Thank you. Rebecca Miller here.

ASSISTANT: Sorry Rebecca Miller, there are no flights reserved on your given name formerly.

USER: Ok, no problem. Thanks for your information.

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