You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Patrick Williams.

ASSISTANT: How can I assist you?

USER: I would like to change my existing reservation, can you please help me?

ASSISTANT: Sure, I will help you out in changing your reservation.

USER: Thank you.

ASSISTANT: Sorry, we couldn't found any reservation in our database by your name.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you for choosing us.