Incorrect debit amount

Words cannot express how upset I am. They keep debiting my account with an amount we never agreed on. Sad part is that I call in monthly to enquire why and all I get is" mam next month we will debit less. I am tired of this and I cannot have my name listed due to their incompetence. All I want is for these guys to stick to our agreement and not to debit a cent more. I do not recommend them for anyone.