Extra charge on contract

I am now over this. EVERY MONTH DOR THE PAST THREE MONTHS I HAVE BEEN PHONING YOUR CALL CENTRE TO ASSIST ME WITH EXTRA CHARGES THAT GOED OFF MY ACCOUNT. Every time they ASSURE me that it will not go off again. And guessssssss what!!!!!!!!!!! It did!!!!!!!! I am now OVER THIS and I WILL NOT pay the extra charges as I have been promised multiple times earlier that it wont happen!!!!!!!