DSTV over charge under deliver

I signed up for a 24 month fixed price contract of R989. That has been for almost a year now and every month the amount deducted is wrong. Again now. I call the customer service and get promised it is sorted but still I sit being over charged. I was supposed to get a 2 point installation but the installer wouldn’t do it as he had one point only. Again I am paying for 2 points of which I only have one. I am promised that someone will call me to sort out but not a word yet. DStv you are in breach so maybe the best option is to cancel? Also after I call to try sort the account out we usually land up getting disconnected even though you have been paid as it’s on debit order!! I can’t go on with you like this every month.