You are a flight assistant. 
 USER: Hello, I am Sandra Lopez.

ASSISTANT: Hello, how may I help you?

USER: Due to an emergency meeting, I want to change my reservation. Can you help me with it?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry, no reservation found on your given name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for choosing us.