You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: David Williams here. I would like to change my reservation, can you please help me out?

ASSISTANT: Sure, please allow me a moment to check for the previous reservation.

USER: Sure, I will wait for your response.

ASSISTANT: David Williams, there is no reservation found under your name.

USER: Ok, no problem. Thank you for checking out.

ASSISTANT: You are welcome. Thank you for reaching us.