You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, do you need any help from us?

USER: Please help me to change my recent reservation.

ASSISTANT: Sure, could I have your name please?

USER: I am David Williams.

ASSISTANT: Ok, please allow me a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes.

USER: No problem, thanks for your information.

ASSISTANT: You are welcome, have a great day.