Form: Justifiant votre inscription au regime auto-entrepreneur?

Please could you advise me re a problem with RSI. I have been a micro enterprise for several years as a professional liberale. In February this year I switched to the régime micro-simplifié starting from the beginning of 2010 and have since paid my first quarterly demand and received my second (from URSSAF) - so all is working OK.

However, I had already paid my first quarter’s cotisations to URSSAF and RSI. I have heard nothing more from URSSAF but continue to receive demands for payment from RSI (I paid quarter 2 after they sent a threatening letter and have just received the demand for quarter 3). I have written to them explaining my situation and have today received a letter back saying that to regularise my situation they need a photocopy of my form P0 justifiant votre inscription au regime auto-entrepreneur. My understanding was that strictly speaking I wasn’t an auto-entrepreneur and I certainly have never seen a form P0 (in fact I have never had any confirming documents apart from the “do not respond” email when I first registered on line in February). This is the only thing they have asked for and I don’t have it - any information would be much appreciated.