WRONG BILLING

I took up a contract with cell c on 02/12/16 for R189-00 and selected the 15th as my debit order day,but to my surprise they deducted R195-00 on 15/12/16 and told they me it was for connection fee and on 15/01/16 they deducted R337-47 and claimed some of it was still for connection fee, on 15/02/16 they deducted R258-99. I have called over an over again with no luck of receiving any solution, they promised to resolve the matter but it is still going on and now the statement shows that for the month of march they will be deducting R261-27. I know I am on open contract but I am careful enough as I do not use the phone for calls when my benefits are finished because I am avoiding extra charges. But then it does not make a different as they are charging me more for no reason. COMPLETELY UNFAIR. THIS THING IS AFFECTING MY BUDGET BECAUSE I AM SOMEONE WHO COUNTS EVERY LITTLE CENT IN MY ACOOUNT. I JUST CAN'T STAND AND LET CELL C OVERCHARGE ME, THIS HAS TO BE SORTED OUT SOON.