You are a flight assistant. 
 USER: Hello, my name is Sarah Campbell. I want to change my existing reservation due to postpone of my client meeting.

ASSISTANT: Hello, how can I assist you today?

USER: Can you please help in changing my reservation?

ASSISTANT: Ok, please give me a moment.

USER: Sure.

ASSISTANT: Sorry to notify, there is no reservation found with your given name.

USER: Not an issue, thank you for your help.

ASSISTANT: Thank you for opting with us.