I have never once gotten a random invalid charge from OVH and it's been years. Do you actually have a 1200EUR VAT invoice with line items from them or was it just a charge out of nowhere?
Maybe a bug or some UX/UI shenanigans, since I also got errors to cancel such invoice and obtain a refund. But since I complained through PayPal they've been acting in bad faith (like contesting my dispute the very last day without getting back to me, or changing the reason why I I'm not eligible for a refund).