You are a flight assistant. 
 USER: Hello. Sarah Hall here.

ASSISTANT: Hello, how may I support you today?

USER: I have made a reservation earlier, due to some issues I need to change my existing reservation. Can you aid me to change it?

ASSISTANT: Sure, please wait for a minute.

USER: Sure.

ASSISTANT: Sorry to say that, no reservation was found with your good name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for reaching us.