STOP DEBITTING ME INCORRECTLY! Now I understand why people make manual payments

I entered into a package contract with 15 months remaining at a set fee, this is the 2nd time I am having to call to get you to debit my account correctly! WHAT PART OF SET FEE ARE YOU NOT CLEAR ABOUT? FIX THE BILLING ISSUE ON THE ACCOUNT!!!! I AM NOT GOING TO CALL EVERY MONTH FOR THE SAME THING! A contract is binding to both parties! I have not nor will I permit you to debit more than what I agreed to. I await my refund. If you bill me incorrectly again for the duration of the contract, you will have breached the contract and I will cancel