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

ASSISTANT: Hello, how can I assist you today?

USER: I need to change my existing reservation due to sudden change in my meeting with clients. Can you please help me in this?

ASSISTANT: Sure, please wait for a minute.

USER: Ok.

ASSISTANT: Thank you for waiting. We are apologize to inform you that, we did not find any reservation against your name.

USER: Ok, no issues. Thank you for the information.

ASSISTANT: Thank you for approaching with us. Have a great day.