Cancelled and stopped paying but Im still Charged

I cancelled my DSTV subscription at the end of July, I want to sell me decoder and now there is a R207 charge for the grace period you gave my in August? Why the hell must I pay that If I was told my service will be stopped at the end of July? You guys are ******* and your customer service agents have no idea. Why must I pay for something that was not explained to me or that I did not ask for. Pathetic