Unauthorized Debitorder - Bad client service

Poor service, my husband is paying membership fee for our son and then out of the blue they start debiting my account with the membership fee. I reversed the payment because I didn't give permission for the debitorder and the amount is totally wrong and it's already been paid by my husband. Now they refuse my son access to the gym. After several mails and phone calls, it's still not been sorted and I keep receiving e-mails and sms that our account is in arrears.