You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: My name is Sarah Brown, I want to change my reservation as my plan to visit Dallas for vacation is postponed. Can you change my reservation?

ASSISTANT: Yes, give me a moment.

USER: Sure.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for contacting us.