What information is RSI asking for?

I received a letter from RSI asking for an officially translated birth certificate. I found an officially sanctioned translator who translated my Canadian province official birth certificate. RSI also asked for a photocopy of my passport (which is British). It did not say that they wanted an official translation of it (although I suppose now that they would want something official). I mailed the original birth certificate, translation and passport photocopies by registered mail (and they were received). Now, I have another letter stating that they want more, but is not really clear to me exactly what they want. I have tried calling them, but their voice mail is so garbled I cannot understand what is being said. So, this is what they are asking for:

Nous vous demandons donc de bien vouloir nous adresser uniquement: L’acte de l’état civil étrangers et leurs extraits ou copies officiels doivent être légalisés ou, le cas échéant, apostillés pour être recevables en France. Le CANADA fait parti des pays dont la législation doit être apposée.

Maybe they thought my British passport was Canadian. Maybe they don’t realise that Canada doesn’t have national birth certificates. Or maybe I should get my British passport copied, translated and notarised? I don’t have a valid Canadian passport at present (due to the expense and short validity). Any suggestions?