You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Sandra Hall, want to change my reservation. Can you please help me?

ASSISTANT: Sure, I can help you.

USER: Thanks.

ASSISTANT: Please wait.

USER: Ok.

ASSISTANT: Sorry, there is no active reservation found with your name.

USER: That's fine, thank you.

ASSISTANT: Most welcome.