回複：買的房子裏CABLE還有,請問如果用是不是違法?

I don't think it's a problem, you are not the one who made the mistake, although you are benefiting from someone else's mistake. If you care about the money, don't say anything; otherwise, call the cable company. Few years ago, I was paying for basic, but was getting standard for many year, I didn't know until I called the cable company for something else, and they found out, they simply changed it back to basic.