You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: May I know your name please to check the status of your reservation?

USER: Myself Sandra Miller.

ASSISTANT: Thank you. Please stay online for a while, I will check your reservation status and let you know.

USER: Sure.

ASSISTANT: Sorry, there is no reservation matching with your name in our portal to make changes further.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for reaching us.