RSI Caisse Nationale VS Province?

Hello there! I have posted this query in another member's message but I would like to seek wider help~

Registered in Sept 1 and having sent out 1 facture already, I got 2 letters from RSI to request for documents so that I can get my first carte vitale. Question is, who should I reply to?

I got requested documents (acte de naissance with translations & apostille, copy of carte de séjour...) from first, RSI Profession Liberale Province (which is correct as I'm doing consulting based in Marseille), and then, another letter from RSI Caisse Nationale asking for the SAME documents. I dunno to whom I should reply really. It's not like that the documents are really easy to get, and with all the apostille and translations needed... I wonder if you have encountered the same situation and what did you do?

I have tried to call the numbers on the letters but always got onto answerphone...

Thanks a lot in advance and all the best!