Unauthorized deductions

I enrolled my daughter for tutoring lessons last year and after I told the support manager that I do not require lessons in December as the school already get closed and the kids have exams in November the deduction was made and I got forced to have the lessons from the tutor. Again they have debited my account in Jan. I do not receive any communication from the support manager and also the phone lines are just busy making it impossible to reach them. I have never signed up for this debit order deduction but they seem to not get bothered. Really frustrating service.