How do I know which business structure I have set up in France?

I’m a EU citizen and about three months ago I registered for business online in France. I thought I was registering for auto-entrepreneur, but as I later discovered, this wasn’t the case. After two months I started getting letters about Cotisations Sociales Provisoires 2016 and after calling RSI in search of an answer why I have to pay that amount of money, they told me I wasn’t in fact an auto-entrepreneur (they checked my Numero de Sécurité Sociale). Told me I was a Commercant even though the nature of my work is far from Commercant. I am a Thérapeute Holistique.

So I called Chambre de Commerce where they explained to me that I was in no way Commercant (didn’t check my Sécurité Sociale) and need to call Urssaf. In the end I didn’t call them but I found a Demande d’adhésion sur la Régime Micro-Social Simplifié on the website of l’Autoentrepreneur where I was waiting for the answer for one month and after several calls I discovered that they can’t do my change if am a Commercant.

What I want is to become an auto-entrepreneur with régime micro-social where I can declare every month/or three months without extra costs if my business income is 0 euros.

1. How do I figure out which business structure I am (auto-entrepreneur, SARL, EURL etc.)? None of the letters that came in have anything like this in them. Furthermore, how do I figure out in where am I in terms of Profession libérale or Commercant? According to societe.com they state something about me being a Professions Liberale, whereas RSI told me I was a Commercant (after checking my Sécurité Sociale).
2. Whatever the structure, I want to be an auto-entrepreneur business in France since I won’t be earning that much money per year and don’t want to have extra costs with TVA. Is that the right structure for me?
3. If it is too late to change the structure for the following year (if I read correctly this needs to be done before 31 October for the following year), would it be best to just close my business and in one or two months open an auto-entrepreneur online? How long does it take to close the business?

I just need some clearance and know in which direction I need to go.