Look through your previous bills. If you don't have paper copies, check the full PDF versions you can get online. There is often a section about changes. Plus, you can compare what services you are getting and their prices. It's likely you were on a promotional price, and that promo price expired.
You can look here:
If your price is lower than those prices, then you're on some kind of promotion. Asking friends and neighbors or browsing this forum is another way to know stuff like this. 2 years seems to be the most common new customer contract period among cable and satellite companies.