Very tardy response to downgrade service.

I have been a user of Vox Telekom's YahClick service for more than two years.<br> In April 2015 I received notice that my current agreement was about to expire.<br> I was offered replacement services which, for almost the same cost, greatly reduced the service I was using (i.e. from a 10 mbps link I would be reduced to 6 mbps and instead of a cap of 45 Gbytes per month, I would be limited to 40 gbytes. Once my current service expired, they would continue to deliver on a month-to-month basis.<br> Naturally, I located an alternative broadband provider and requested that they downgraded my service to their minimum offering (to utilize as a backup ISP) on October 1st.<br> In November,they again exercised my stop order to deduct the full cost of the 10 mbps service I stopped utilising at the beginning of October.<br> Although I have received automatic notification of my queries lodged concerning this matter, and \read notices"that they have read my mails"