Extremely dissatisfied client

I have never received such bad service. This service provider’s product never worked at my place. I was constantly at their offices trying to resolve connectivity issues. They even made be buy another device claiming it will work better. I canceled the product and installed fibre. Now they are claiming I owe them. I had a month to month contract with them and when I did not pay they would disconnect me. Can they stop debit my account for a service I no longer use