For anyone who did AOS: there is page in the Notification Letter thas says - if you do AOS rather than CP, send $100 to Department of State as a Visa Processing Fee. This is in addition to the $385 fee that I sent to USCIS. The address that they give for $100 Fee is in Pittsburg, PA. My lawyer advised me to send this once I receive the receipt that my AOS was filed. So, I did it. In 1.5 week, I got the whole thing back - it came back from KCC, saying they don't take payments for the processing of immigrant visa's petitions. So, it's confusing: they thought I sent the fee for AOS application in the wrong place, while I was sending visa fee, as instructed. Or maybe my lawyers instructed me incorrectly and I should only send the visa processing fee when my AOS is actually approved rather than just filed. Please share your experience. Thanks