Cell C *****ing from us

i was charged R5052.31end of November which I paid and stopped using cell c sim card beginning of November. this month in December they just decided to deduct R952 from my account and when I called their contact centre the lady assisting me just said what was I expecting since m using their number and told her haven't used it. cell c is the worst network provider in South Africa. if using it, run while you still can cause their service is very bad.