You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

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

ASSISTANT: Sure, can you please let me know your name to check with the reservation status in our database?

USER: Shirley Roberts.

ASSISTANT: Sorry, there is no active reservation found under your name to change.

USER: No problem, thank you.

ASSISTANT: Thank you for reaching us.