You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: I am John Wilson, can you help me for changing my existing reservation?

ASSISTANT: Sure, please wait for a moment to check your details.

USER: OK.

ASSISTANT: I have found your reservation, can you help me with your new airport codes?

USER: My airport codes are LGA to MSP.

ASSISTANT: May I know your dates?

USER: My travelling dates are 02/08 and 02/10.

ASSISTANT: Please wait for a moment. Sorry, no flight available for you on your requested dates.

USER: Oh! It's ok no problem, thank you for your services.

ASSISTANT: Thank you for choosing us, have a nice day.