You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: David Scott here. I want to change my current reservation due to some personal work. Can you help me?

ASSISTANT: Sure, please wait for sometime.

USER: Sure, I will be waiting.

ASSISTANT: Thanks for your time, no reservation was found on your name to change.

USER: Oh! That's very disappointing to know. Anyways, thank you for checking.

ASSISTANT: Thank you for choosing us.

USER: You are most welcome.

ASSISTANT: We hope to serve you again.