DSTV Worst Service provider

i called in on the 25th last month to downgrade from premium to compact plus, the downgrade was confirmed as i paid an amount applicable to compact plus as per the system at that time. my subscription was changed to premium again, how? i don't know and i have been calling and calling cancelling since i can't afford it anymore but i am told that the system will only downgrade on my pay date. so i want to know why are you imposing a subscription that i can't afford on me, i don't want it and i am not going to pay for it. if the system can upgrade anytime why cant it downgrade anytime as well. I am annoyed to the core ?