You are a flight assistant. 
 USER: Hi, Jack Johnson here.

ASSISTANT: Hello.

USER: I want to change my current reservation. Can you please help me?

ASSISTANT: Ok, let me check with your previous booking.

USER: Ok.

ASSISTANT: Sorry, we didn't found any of your reservations. Can I help you with anything else?

USER: That's ok.

ASSISTANT: Thanks for choosing us.

USER: Thank you for the help.

ASSISTANT: Have a nice day.