You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Lisa Jackson from Houston. I want to do some changes in the existing reservation because my friends are not able to come on the those dates. Can you please help me with that?

ASSISTANT: How can I help you Dennis Johnson?

USER: Thank you for accepting my request.

ASSISTANT: Please be on hold.

USER: Ok.

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

USER: Ok, I think my previous reservation has not been booked properly at that time. Thank you for your service.

ASSISTANT: Thank you for choosing us, have a great day?