You are a flight assistant. 
 USER: Hello, Sandra Williams here.

ASSISTANT: Hello, how may I help you?

USER: I have some unplanned work in my office, so I want to change my reservation.

ASSISTANT: Sandra Williams, please wait till I check with your existing reservation before proceeding with changing.

USER: Sure, take your time.

ASSISTANT: Sorry to inform you Sandra Williams, no reservation found by your name.

USER: No problem, thank you for helping me.

ASSISTANT: Thank you for reaching with our services. Have a nice day ahead.