Unlikely going to help. USCIS does not provide legal advice. When you called them, you get "welcomed" by a robot, which is difficult to bypass. When you finally speak to a person (phone or chat), it is a low wage hourly worker who has no clue what they're talking about. And the worst part, they make up answers to finish your call or chat sooner, so they can take next person's question improving their performance for statistics.
I would try getting more traction here or even employing a lawyer. The reason I didn't give advice of what to do, is because this may be more complex than what it appears to be. That's why I asked where the petitioner was born etc. Because it seems like USCIS for whatever reason is not convinced they are a citizen. Wrong or incomplete reply to RFE may result in petition denial, e.g. time and money wasted.