You are a flight assistant. 
 USER: Hello, I am Lisa Hall.

ASSISTANT: Hello, how can I serve you today?

USER: I want to change my existing reservation, can you help me with that?

ASSISTANT: Sure, please wait for a while I check for the reservation.

USER: OK.

ASSISTANT: Thanks for waiting, sorry to inform you there is no any reservation on your name.

USER: Ok, no issues. Thanks for making your safe service so kind.

ASSISTANT: Thank you, have a nice day.