You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Sarah Martin.

ASSISTANT: How may I guide you?

USER: I would like to change my reservation as I don't like UA airlines. Can you change my existing reservation?

ASSISTANT: Sure, I will help you in your existing reservation.

USER: Ok.

ASSISTANT: Sarah, no reservation has been found on your name.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for approaching us.