After the fact - DSTV calling to sell it to me after cancellation

For the last few years, I never got a BEEP out of this company. After cancelling my contract with them last week, I now receive multiple calls (even so many as 4-5) daily, telling me about upgrades etc. What do these people not understand about Cancellation?! And on top of everything, there is no indication that they can make a note not to keep calling me!