You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello,.

USER: I am Sarah Adams.

ASSISTANT: How may I assist you?

USER:  I want to change an existing reservation due to my meeting got preponed. Can you help me out?

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: I'm sorry, there is no reservation by name Sarah Adams.

USER: Ok, not a big problem.

ASSISTANT: Thanks.