Google translate of the letter:
Thank you for your message. Your order from 18-03-2015 12:43 (payment gratefully received) included a recurring delivery service.
This was clearly stated on your bill and on the website, with your first order. On the next delivery date has been advised of your bill. Since we have received no notice of the Services by you, this mission has been sent.
Shipments of recurring delivery services are each about a month after the original order date (exact date, refer to the bill) Sent. The recurring delivery service is not binding and therefore can be canceled at anytime. Cancellations must be on time (the exact date can be found in the bill) receipt by our customer service team to stop the monthly mailing. Your recurring order takeaway is considered terminated as soon as you receive a cancellation confirmation email from our customer service.
My takeaway was not automatically terminated for example, receipt of your return shipment. You must enter separately in writing via email to the customer service your cancellation known.
All other shipments, after the first delivery are not considered as online purchase and can therefore, after the goods have been shipped from our warehouse, not be returned.
I can cancel the subscription / recurring delivery service as soon as possible, which is considered as a confirmation of the cancellation."
The letter sounds pretty straightforward to me. You inadvertently signed up for multiple shipments. This happens from time to time, where the default box of "Yes! Send me shipments every month!" is checked. Good luck finding the box so you can uncheck it, though.
It sounds like the letter is offering to cancel the recurring subscription, so I recommend you take advantage of that. You might still be stuck with the bill for the shipments already received, but then you'd (hopefully) be done with this expensive lesson. Always read the fine print, on every page. The order page where you put in your address probably had some text that said if you don't want to use a credit card then they will bill you. This is quite common in Switzerland.