You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: My friends are planning for some other trip, so I want to change my existing reservation. Can you help me?

ASSISTANT: Sure, let me know your name?

USER: My name is Barbara Smith.

ASSISTANT: Sorry Smith, I couldn't find any reservation on your name.

USER: It's ok, thank you for your time in checking my reservation.

ASSISTANT: You are welcome.