You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is William scott. I want to change my existing reservation, can you help me with that?

ASSISTANT: Sure, please give me a minute.

USER: Sure, take your time.

ASSISTANT: Sorry to tell you that, there is no reservation found on your name.

USER: Ok, no problem. Thank you for assisting me.

ASSISTANT: You are most welcome Scott.