You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Dennis Lee, want to alter my reservation. Can you please help me?

ASSISTANT: Sure, please wait for a while.

USER: Sure, take your time.

ASSISTANT: Sorry Dennis, there is no active reservation found with your name in our records.

USER: It's ok, thank you.

ASSISTANT: Most welcome.