My account is always overdue even after paying

Its not even a year that I subscribed to price lock ,every time they debit incorrect amounts and disconect my dstv.Whenever I phone I always speak to different people then they always say the must b a mistake on their side.I pay my dstv every month as agreed bt feel that im not treated fairly as client I even stopped the debit order and now make cash payments as they keep inconveniencing me on my bank account