You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: Due to sudden change in my present schedule I want to Change my existing reservation. Would you help me in doing that?

ASSISTANT: Sure, can I know the name on which the reservation has done previously?

USER: Myself Rebecca Jackson.

ASSISTANT: Please give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no reservation available on the name Rebecca Jackson.

USER: Ok, That's fine. Thanks for checking my details.

ASSISTANT: You are welcome.