You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you today?

USER: I am Helen King. I would like to change an existing reservation that has been booked earlier this week.

ASSISTANT: Please give me a moment to check.

USER: Please take your time.

ASSISTANT: Sorry Helen, there is no reservation available in our database on your name.

USER: No issues, thank you for the information.

ASSISTANT: You are most welcome Helen.