You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Owing to an emergency, I want to change my existing reservation. Can you please help me with this?

ASSISTANT: Ok. Let me know your name to check for existing reservation.

USER: Margaret Lopez here.

ASSISTANT: Please, wait for a while.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no reservation found on your name to change.

USER: It's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.