Instead of blocking prepaid cards, why not work on your product to give them a reason to buy again the month after?
You guys talk about credit cards and stuff. They are CUSTOMERS. Work on your product and make them happy and they will buy again the next month.
You want your customers to be with you longterm because they forget to cancel or because your product is so good that they stick around?
If your business model is to rely on people forgetting to cancel... your problem is poor business fundamentals, not pre-paid cards.
