Here's a quick view our sales on one of our sites in January. While it may look eratic, it's really not as it coincides with our regular traffic + content offerings of the day. My point is, sales trends change for all kinds of reasons. Its unlikely that CCBill is changing anything.
Have you considered comparing your traffic to your daily content or teases, to your sales, and your denials? That may give you a better explanation and help you to pinpoint what is going on.