Duducting more money on my fibre contract without any agreement

I have had fibre with them for over one year now, they busy now ducting more than agreement contract no communication, when I call they said they will get back to me still no explanation of why they duducting more money from me, ref no SR*** worse service how do you deduct my money with no explanations and how do you change our terms of agreement with no agreement with your customer day light *******.