You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I am Andrew Brown. Can you help me for changing my existing reservation, because while booking in my previous reservation I gave wrong airport codes?

ASSISTANT: Sure, just a second please.

USER: OK.

ASSISTANT: I am sorry no reservation found on your name. Thank you for choosing us.

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