You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I serve you?

USER: Actually I made a earlier reservation to go for a trip with my friends, but heavy work  in office I want to change my reservation. Can you help me in changing an existing reservation?

ASSISTANT: Sure, may I know you good name please?

USER: I am Brain Brown.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Thank you for waiting. Unfortunately we didn't found any reservation matching your name.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for choosing us.