You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I am William Turner. I am planning to change an existing reservation, due to some urgent work. Can you please change my reservation?

ASSISTANT: Sure Turner, can you please wait for sometime. I will check your reservation details and get back to you.

USER: Sure, take your own time.

ASSISTANT: Sorry Turner, I have not found any reservation by your name in our database.

USER: That's fine, thank you for your help.

ASSISTANT: Thank you for contacting us and have a good day.