Here's how the process works -
For CP - KCC receives the DS260 form, process it, schedules the interview with the applicable embassy and subsequently forwards the KCC file to the embassy. Once the KCC file gets forwarded to the applicable embassy, KCC no longer has anything to do with the case (for situations where a selectee needs to change the embassy for one reason or the other) at that point.
For AOS - KCC receives the DS260 form (if submitted) and adds it to an applicant's KCC file (DS260 does not get processed). KCC waits for the IO from the applicable FO to request the applicant's KCC file, the file gets forwarded upon request, KCC no longer has anything to do with the case once the case file gets forwarded as requested.
So since the KCC already forwarded your KCC file to your IO, they can no longer schedule you for a CP interview AFAIK. However, if you're (1) able to directly reach out to the embassy you're hoping to interview with, (2) explain your situation, (3) convince them to take on your case, (4) get them to request your KCC file from your USCIS FO, and (5) schedule your CP interview, - then you may have a shot at switching over to CP.